Try one of the Habitat for Humanity ReStores. There's one in Randolph. I'm not sure if that's close to you or not, but there are a few others. They sell just about everything for building and finishing a home (at a much cheaper price), so I don't see why they wouldn't have (or couldn't help you find) some Corian. :-)

I think it will be difficult to find unless you get friendly with a professional installer of that product or similar products. There seems to be some unwritten rule maybe from the manufacturer that it does not get sold to DIYers and the scraps are somehow disposed of quietly. I guess that is the way for it to keep quality control on the finished product. There might be someone hawking it on craiglist or depending on how much you need, maybe get a "corian-like" cutting board and use that. Good luck.