I really like the mug with gelt
I agree he probably has a Menorah. I was thinking more along the line of candles, like the ones sold at BB&B for $10, minus 20%
Maybe a bag of parce or Vegan gelt and a couple of inexpensive dreidels
I found vegan gelt at our health food store! I agree that a menorah is too personal, and I was pretty sure Hanukkah is not as important as High Holidays, but I so appreciate the input, it really helped. 
@greenbutton You’re a very nice person! He’ll be happy surprised.
That’s very sweet of you. I also agree that a menorah is not appropriate. However, I love the idea of the mug, with or without gelt. It’s something he can use in the office all year round. It’s not too personal or intimate and it’s not so expensive that it would make the young man feel obligated to reciprocate.
I agree no menorah for the reasons posted. Personally, I wouldn’t want the mug because, once Hanukah is over, I probably wouldn’t choose to use it, at least in the office. I think a card with good gelt (Sees, for example) is an incredibly thoughtful and appropriate gesture for a co-worker.
^You could just get a plain eco-friendly travel mug for the gelt.