We have a lightly used waterproof mattress cover available for free. I don't recall if this fits a queen size or full size mattress (it hasn't been used in some time), and unfortunately it's not labeled. This was always used with a fitted sheet over it. No stains. Smoke-free home.
--
Guisou Zarbalian, MS, MPH
(she/her)
guisou @ gmail dot com