Red is usually on aftermarket distributors like MSD or Mallory. The Chinese MSD copies also have them. However, they will not work with a stock distributor.
I don't find any in a brief search. If you are using a '57 or newer distributor, look for a cap for a small block as it is the same.
If it is older than '57, try some red spray paint. If there were ever any red ones made, you probably won't find one at this point.
Lawrenceville, GA