Not sure if this is cool, but I was literally just about to post this question, but you're post is the newest so didn't want to post a dupe right next to it.
I was just considering grabbing something like this and this.
I'm looking for something hypoallergenic so I figured foam would be the way to go, not sure what kind of depth would be required or what type of brands are good/bad. The two I found on amazon seem very well reviewed and pretty cheap, although I'm not sure if you need a box spring with foam mattresses.(Ideally I would like to avoid this)
So, questions: