OK, since no one else have answered...
If my memroy serves, my brother bought a holster made for a Python and stuffed his GP100 in it a few years ago, but it was a very tight fit. I think the leather stretched enough to make it usable for him - that is range use, not duty or other social situations.
So I guess my answer is: I think it will fit, sort of. Not a very good answer nearly two weeks after you posted, but if you're still interested in the holster, maybe this is better than nothing.