Just wanted to post and update to this. So far in my search Calsak Plastics has the best prices. They do have a $25 per order cut fee, but offered to wave that if I purchase 5 or more full sheets... or once I establish my self as a repeat customer. Even with the fee, they are several dollars cheaper per 12x24 sheet across the board. And compared to where I was buying before, nearly half the price
Thanks to everyone that offered up sources.