I know eBay is considered a 4-letter word by some, but I've gotten some great deals on vintage Don Hume leather. The Boarder Patrol design made famous by Bill Jordan is the Don Hume H216. You would want the No 7 4" to fit your Python (7 fits a medium/large frame and the 4" is the barrel length).
And for general info, sizes of the H216 are as follows:
No 1 - K Frame
No 2 - N Frame (also fits my King Cobra pretty well)
No 6 - not cataloged, but supposedly same as a No1
No 7 - L Frame, Speed Six, Python