I've been collecting Saginaw shafts and now have a few too many. These are genuine Rover Australia but are about 6" longer than the front for a Series III 3.5/Stage One.
About $50 each depending on which one. They have various problems, from universal joint wear to slip joint problems.
After getting stung on the last one I had replaced, I've just been hoarding parts. I haven't managed to find anyone that does cheap drive shaft repairs or is into Land-Rovers.
Try a standard 110/90 v8 front prop, but you will need to change the output shaft. These are fairly cheap and i ahve doen it to mines the original double knuckle job broke, after two of Craddocks pattern ones going as well I agve up on them.