Gary,
you need to see if they have a blueprint copier. If so, they can copy 30" sq. no problem.
I was just at my Staples this morning, they have one. The recommend calling before you come so they can have the unit warming up. It's not usually left on since it is used infrequently, and takes 10-20 minutes to warm up.
If not, you'll have to do it in 11 x 17 size and tape them together.