Consumer Reports current issue has a feature on mattresses. It may be helpful.
As for other hotels that sell their mattresses, W hotels does (or did).
Question for posters: Why is it necessary to replace a box spring when you replace the mattress if it is of solid construction, and simply forms a foundation?
Many mattress warranties will be negated if you don’t have a new foundation, for one.
Mattress warranty? Lol. Please ship it to us at your own cost so we can inspect it and ship you a new one of this one is defective. 
Or even a stores exchange policy. We recently exchanged a new mattress after several months for a different one - full compensation. They wouldn’t have done it without a new foundation as well.
Foundations are fairly cheap vs. the price of the mattress itself.
Sure that they are not expensive. Just read the fine print re: who pays for shipping, and whether the store or the manufacturer takes care of the replacement.
We have been sleeping on our new Tuft and Needle for 2 weeks and love it. My sister has a Leesa (sp?) and loves it.
I have seen the commercials for the Leesa and they even have a try it for free offer. Good to hear that your sister loves it. I am going to look into it again.
Saatva does too. I’m not sure about Bedinabox mattresses.