Try a cabinet shop or a regular lumber yard/building supply house, they purchase plywood from distributors that carry ACX FIR and Marine Grade Plywood. They aren't real busy right now, might find a dealer willing to sell you a few sheets on the cheap. If you were closer I could set you up with the Marine Tech PTP KDAT for around $60.00/sheet. ACX FIR is running us $33.53/sheet if I buy a few pieces. ABX Marine Plywood from Plum Creek is $76.32. Marine Tech is cheap because I purchased many moons ago and plywood has been trending up as a commodity. Richie Rich has a point, in the long run what is an extra $100 gonna mean. Lots of ways to go, Aruaco plywood is good stuff too.

Update, ACX Auroco Mill just burned and the prices will be going up tremendously. A tidbit of info I did not have this morning.

that sux better get to 84 tomorrow or pro build and check them out