Hi!
I'm new here and "Mark, father of EJ" pointed me to this thread.
This web page has all the possible cushion/pillow ideas in images on one page. I have tried the "Neck Pillow" and the "Pool Noodles", both with the opening to the back.
My pain is mainly to the back. It is still difficult to sit for longer than 10-15 minutes, but I agree they are a big help. Perhaps if I had some disposable cash besides the essentials I could find a better solution from this page. This has affected my ability to work to the point I can barely pay rent.
Coccyx cushions and supports
w w w .coccyx.org/coping/cushions . h t m
I will come back after 15 posts and fix that URL, but in the meantime, that link is well worth visiting.