There was a aftermarket hammer available
Brownells used to carry the Moulds company replacement speed hammer for the Number 1. You could contact Moulds and see it they will sell you the set. It comes with a speedlock or competition replacement hammer and a wolff replacement heavy weight hammer spring. The cost for the kit when Brownells offered it was either 55 or 75 dollars depending on which kit with the competition being the more expensive one. I had contacted them once on a replacement quarter rib scope mount for my Number 1 and they were willing to sell it to me. Expect the price to be higher than when it was listed by Brownells.