I use a Celtic design stamp on all the arrows I make and it does the job of identifying my work.
While I use a pre-made design, you can get custom stamps through about any stationary store or stamp art store.
While a stamp is good for my arrows, I agree with folks that handwriting is better for bows. Problem is a lot of folks have pretty hideous penmanship these days. You could probably find someone that practices calligraphy or just has good handwriting and have them do the script for you at a pretty reasonable price. Heck, if it's someone in the archery community just give them one of your prototypes in exchange for 20 years of writing on your bows!
Guy