I don't know why I didn't think to look on Amazon. I think this will be the first try:
https://www.amazon.com/TISHIJIE-Adjustable-Inflatable-Lumbar-Support/dp/B096TGN47J/ref=mp_s_a_1_4?crid=OZZ8SLBRS2PT&keywords=inflatable+car+lumbar+support&qid=1654646279&sprefix=inflatable+car+lumb%2Caps%2C123&sr=8-4
If that doesn't work, I'll try this one. Maybe I can replace what's inside the seat with it.
https://www.amazon.com/Heycell-Inflatable-Ajustable-Orthopedic-Wheelchair/dp/B08JCKNZB1/ref=mp_s_a_1_5?crid=3RD8PN1RZR3DB&keywords=inflatable+car+lumbar+support&qid=1654646414&sprefix=%2Caps%2C128&sr=8-5
No openings in the seat back. They are bucket type and stapled shut. I'll have to remove the entire seat to work on it. I'll try the easy way first. We have a 6 hour drive to Virginia in a few weeks and I'm trying to make the trip a little easier on the body
