I think Lowe's cuts plexi glass for free, but I can't say for sure. Our Lowe's has the poorest customer service. I bought one of the knives to cut the stuff myself (I have not cut it or done anything with it, yet). That's what I bought it for, quilt templates. It really wasn't expensive. I can't remember how much it was bc I've had it a while. I think one 8 x 10 piece was around $2. The larger the size, the more it costs...BUT if they will cut it for free, you might be better off (and save money) having a larger piece cut into smaller pieces...more for your money. Maybe have leftovers for templates for another project...???
Call your local hardware store and see.