Most prop Mfg's are happy to meet whatever spec you require. Call them and let them know what you want and the pitch.
Measure the mounting bolts opposite of each other (center to center of the bolt heads).
I'm guessing looking at your photos that it is SAE-1...that is 4.375"
The larger size (probably not used on your prop is...
SAE-2...that is 4.75"
M-M.