A queen mattress we had in a second quest bedroom that we're converting into an office. It was kept under a mattress cover and only slept on eight to ten nights (hence the conversion into a home office).
The mattress is firm, but not hard. If you don't have a way to get it to your home, we could deliver if it's in Boulder county.
We also do have a very heavy-duty steel bed frame, but no box spring.