My apologies for not replying earlier - I just noticed I had a message!
We have a local cabinet shop who does commercial & residential countertops. In my initial research, I called them with the idea that I'd have them build the countertops but I'd do the installation. As it worked, out, they didn't want to touch anything "RV", but the owner suggested I could browse their remnants for any material that I could use. He offered the larger pieces for half their cost, and small stuff for free.
I'd also found businesses online that sell overstock; prices are based on 1 to 5, then 6-up, if I recall. They stock the standard sizes - 30"x6' and 12', as well as several custom sizes. Their prices were similar to what I paid at the cabinet shop.