Easy enough to make, use a piece of 3/8 inch steel tube,about 4 inches long, cut or file a couple tabs in the end to fit the notches in the firing pin, drill a cross-hole in the other end to use a screwdriver or bar as a t-bolt.
Usually the firing pin unscrews fairly easy unless it has a burred thread at the end where the lock screw is installed (and don't forget to remove the lockscrew first) .
Of course I had to be difficult and make one out of a JR RC Helicopter mainshaft... only because I didn't have a piece of 3/8 tube handy.