By far your best option is to send it in to Colt.
Colt "probably" still has hammers and they're the real experts on Python repairs.
There are few others I'd trust with such a valuable gun, and none of them are likely to have a hammer. They'd want you to supply one and stainless Python hammers are pretty much unavailable.
When dealing with Colt's especially Pythons a BAD move is to take it to a local gunsmith. Almost none of them today have any idea of how the old Colt action works, and you run a good risk of getting the gun back with other problems.
I'd contact Colt about this.
Info is on their web site: