I'm also making pewter plaque belts. Prices vary depending on size and options, but generally they are $8.00 per plaque without enamel coloring and $9.00 per plaque with coloring. The plaques are between 1 1/4" and 1 1/2" square and have pegs cast into the back that I attach them to a sturdy leather belt with. In the future I will also be offering completed woven belts for women and buckled style belts with 14th century belt mounts. Here are some examples of completed belts:
This one was based on an effigy brass from 1380.
http://i538.photobucket.com/albums/ff347/isabellaevangelista/1380Closeup1.jpg
This is the first belt I made for myself originally:
http://i538.photobucket.com/albums/ff347/isabellaevangelista/mykit/finishedbelt1.jpg
They have a fermail style fastening instead of a buckle. Also I am willing to do custom mold carving for an additional cost.