I did think of something.

I used to have a kitty bed for Scooter Bug, that was really just a big square. The thing that was special about it was that it was supposedly "self warming" so that it was better for kitties with arthritis and other ailments. Scooter Bug loved it! I don't know how 'warm' it ever got, but I do know he laid on it all the time. (LES, gosh I miss him.)

It was sort of like this one:
http://www.amazon.com/Solution-Self-...1480517&sr=8-4