Pauly,
You might try hitting a junkyard and looking for a wrecked well-optioned car with adjustable lumbar support that you can scavenge and at least temporarily rig it for the trip. For instance, I've had a number of cars that had little air bladders (GM, I recollect), and I think some Japanese brands had a rotating cam-like assembly. Memory is a bit sketchy.
See you in Luray.
There's also something like this:
Lumbar Support Pad
