There are are a bunch of national chains that use computerized output devices to do finished vinyl signs for about $6.50 per square foot or about $60.00, for yours. The local one I use for all my clients is "Instant Signs". They also have a material called Alumalite, which is a foam center and thin aluminum cover in many colors. It's rigid, but dosen't "dog-ear" like foamcore.

If you get vinyl you'll want to edge it, and roll it with the graphics inside for durability. You could either use grommets or velcro. non-industrial velcro can be peeled off of keyboards without damage.

Russ