Agree that a banana is eating to eat and fills you up.
I have the same problem at work, not hungry at 6 am, ravenous around 10 to 11, no lunch till later some days. Regarding yogurt, there are a zillion types these days. Greek yogurt is higher protein, comes in many flavors, and can be eaten quickly. Though I avoid wheat, some grain also works. The best would be a tortilla with egg and a bit of spinach and cheese inside. In my dreams I’d make that to take to work. Apple and low fat cheese. TJ’s makes a sliced Jarlsberg Swiss that is delicious and low calorie. Though the low cal thing only works for so long. I find I really need calories and volume at that time of day.
We make big batches of low-carb flax seed muffins with pumpkin seeds and stick them in the freezer. The taste is a huge disappointment for something cupcake/muffin shaped, but they are edible and serve the purpose. I usually just thaw them and eat them cold. W heats hers up.
I also keep Premier Protein bars in my desk and eat about 1 per week. Same deal, they are not as good as the sugary ones.
I don’t eat first thing in the morning usually. Breakfast is mid-morning or a bit later. I like to have some smashed up baked potatoes, cut up hard boiled eggs, and salsa.
If I’m in pinch, like today, and there are no hard boiled eggs in the house, the potatoes and salsa alone will do the trick. I don’t know what it is about potatoes and me, but they are so satisfying and I don’t feel hungry for hours afterwards.
Sometimes instead of baked potatoes, I’ll roast diced potatoes and red onions in the oven, making enough that I can use it for breakfast all week.
Hail the mighty potato! 
I would suggest:
- Cheese, fat is good, fat is not our enemy, neither is saturated fat. Olive oil is fat, with more than 50% of saturated fat to boot. Fatty fish are good for the mind and heart. lol.
- if you don’t mind the taste, canned sardine (in olive oil) is delicious and filling.
- organic whole milk plain yogurt, and if you like Greek yogurt, even better. It is extremely easy to make yogurt at home, pass it through a cheese cloth you get Greek yogurt. Mixed it with fresh fruit of your choice (peach/berries are my fav).
- avacado slices
- hummus dips with carrots/ cucumber/peppers/celery/apples etc.
I think cubical land dwellers would not be happy with sardines in the next cube…
I have an office, but I am sure my colleagues will throw me with the sardines out of the window if I decide to snack on them… 
Lol. Do canned Sardines smell bad? It is delicious :)) the six-pack version at Costco is a good buy. Get a pack for your cube mates!
Yes, most cheese is not healthy way to get your protein, unless it’s the ricotta variety. And watch out for the sugar content in most yogurts. If eggs are out of the question, then @doschicos suggestion of oatmeal is/was excellent. Here’s a variety I have found to be low sugar, low “good fat” and high(er) protein, lots of seeds:
String cheese, almonds or other nuts, olives, yogurt
Nut allergy.
It’s too bad you’re allergic to nuts. There are other options though.
I like hummus & fresh vegetables or cheese and fruit. Oatmeal is also good and you can add different things every day to make it interesting. I like yogurt, but I usually have to add something like granola or fruit to make it more substantial. Cut up fruit is also filling.
Here’s a healthier homemade granola I make by modifying a standard granola recipe:
- replace nuts with unsalted sunflower seeds
- use unfiltered local honey in half the amount called for (it’s expensive but the stronger flavor of the local honey means you can use less and you get the taste without the overwhelming sweetness)
- coconut oil in place of regular veg oil
- add 1/3 to 1/2 cup of ground flaxseed per each cup of oats
- chopped dried fruit as desired
I get that some people don’t like yogurt. That’s ok. (however have you tried really whole milk plain yogurt dressed up? Fresh fruit, a little honey, and a nutless granola??)
To each his own, but I really want just about everything I eat to be quite good and satisfying. Your body hasn’t eaten for hours - if it’s quality nutritious food (like good cheese, whole milk yogurt, hummus - whatever) don’t worry about the calories - just monitor your portions.
I do not eat before I go to work. My routine is get up, shower, dress, walk the dog, feed the dog, grab my breakfast AND lunch from home and off I go. I get to work at 7:30 - work for an hour or hour and a half, then take a break for breakfast - I want it to be a GOOD breakfast! A can of yoplait would not do for me!
OP isn’t asking for a full breakfast - I don’t think - BUT the snack should be quite satisfying in taste, quantity and satisfying your hunger until lunch.
My normal breakfast before work is low cal/high protein yogurt sprinkled with cut up strawberries, chopped walnuts, and organic granola. That doesn’t sustain me quite so well as a high protein meal like ham and eggs would, so mid-morning (about 3 and half hours after breakfast) I fight off hunger with an apple or orange. That lasts me until lunch
I eat breakfast at home and at work I might much on almonds although that isn’t helpful if you have a nut allergy. I always bring an apple or a piece of fruit or some grapes, not that they are a protein source. I know they are more like a snack but i will sometimes have a granola bar as better than other things I can get out of the vending machine. I have a co-worker who snacks on cut up peppers as well as popping a bag of popcorn at home that she has unbuttered and unsalted.