I'm out shopping and I see the stuff for winterizing swimming pools is going on the shelves. Included in that are "pool pillows" which are vinyl inflatable pillows I guess are for keeping a pool cover off the water over the winter.
So I buy a mid-size one 4'x8', take it home and blow it up. The vinyl is a lot thinner than like pool toys, but it's really flexible and bouncy. I think I've got my new favorite inflatable toy.
These things all seem to come 4' wide and in various lengths from 4' to 15' long. They only come in one color, but since blue is one of my favorites, I don't mind.