Your links gave me more ideas to search for
a variety of assistive tools & diability aids


http://www.lifesolutionsplus.com/
http://www.betterlifehealthcare.com/index.php


I haven't found a good pillow or neck/back cushion for in the tub-
so i think I will just pick up one of those rubber/padded { closed cell foam??} yoga/exercise type mat and cut it to fit.