Hi sanman,
It’s unfortunate that they didn’t have a larger selection at the store you visited. The only suggestions I can make would be to call the other stores that are within reasonable driving distance to find out what they have available on their floor before you go there, to test some of the other options you have available in the area, or to consider some of the online options you have available to you.
If you are uncertain about whether a mattress is or would be a suitable choice for you in terms of PPP then the options you have after a purchase would likely become a more important part of your personal value equation so you can use your own sleeping experience to decide on whether a mattress is a good match for you and still have good options available if it isn’t.
Phoenix