I have a pair of seats that came out of my KVA (I switched to Superformance seats). They are quite narrow in the butt, although I think they are the fiberglass shell type that came with a KVA. I can dig them out and take a couple photos if you like, but I'm just about to head to Canada for the week so it will be next weekend.
I doubt you'd want to travel to pick them up though, they are in Reno, NV, but if you want them they are yours for the cost of shipping. I have no idea how much that would be or whether worthwhile.
Cheers,
Julian