You have a long bed on that double cab? I hope so.
Anyway I dropped a Leer 100XR shell on and put in a Bedrug Bed Mat in my Access Cab. You can get a Bedrug for the entire box - bottom, sides, tailgate - but it cost over $300. I just got the bed mat which lays on the bottom and later I added the tailgate cover (soft sitting).
Get the one for a truck without a bed liner (stock composite bed counts as no liner). It fits into the grooves of the bed, and in and of itself is very comfy, but we toss Thermarests on top for added softness. But any good closed cell foam on top would be excellent. Plus you can pull the whole thing out for cleaning.
The two of us and our dog sleep very well.
Here's a link... Note that AutoAnything
does NOT list this as available for 2010 Tacomas. So choose 2009 (it's the same thing and fits perfecty).