pkoffler,
Numrich (Gun Parts) in NY carries some and always has new supplies arriving that might not be in their catalog. They're worth calling any time you're looking for parts.
Brownell's can also give you some direction on finding parts if they don't have them.
Have you tried contacting the importer of the Chinese-made 1907s? They might be able to get your part(s) and then you could do the fitting.
Good luck,
Paul