Try your local sign shops. I think you can get a sign with the vinyl lettering (one color) starting at $13.00 a foot. I believe they start at 4 feet tall, then you calculate how many feet wide you need by the price. I too was wanting to do something like that, however believe that this year we are just going to go the old fashioned way...... hand made .
Our PTO would like to purchase a few banners before school opens. One can be a generic Welcome to our school....the other we would love to have custom with our PTO logo. Any ideas where to find inexpensive, good quality banners.