I buy mine on Amazon. They're cheap and come rolled up and expand into a totally normal mattress. Not sure what price point you're looking at, but for $140 this is pretty decent.
This one is 2' thicker, and only $209 -- good reviews also
https://www.amazon.ca/Zinus-Hybrid-Green-Spring-Mattress/dp/B06WVNBMD2/ref=as_li_ss_tl?crid=VG98IVE7ZSZU&keywords=queen+mattress&qid=1567889371&s=kitchen&sprefix=queen,aps,177&sr=1-10&linkCode=ll1&tag=glitzandgf-20&linkId=45652e5a1e0681e26b51c837394483c6&language=en_CA