How about this? You register, & then if I ever hear of your original fender tag, broadcast sheet or other paperwork I call you right away? That is how the registry works.
I have stuff here for cars with fake tags. I do not forward anything to car owners who have tried to fool me (or others) with them. I'll save them for the next owner.
If you are desperate for a fender tag to fill the space, please consider one like this;
REWARD FOR MY
+ ORIGINAL FENDER TAG OR +
OTHER DOCUMENTATION
Call 555-555-5555
JS23 N0B 154###
It never hurts to try, great advertising at car shows.