Aircraft Spruce offers sealed universal joints in several sizes.
PN MS20271-B6 is 3/8 OD, .372 ID
-B8 is 1/2 OD, .495 ID
-B10 is 5/8 OD, .620 ID
-B12 is 3/4 OD, .745 ID
-B14 is 7/8 OD, .870 ID
Pricing ranges from $67.85 ea, to $87.85 ea.
The shaft you could get at Metal Supermarkets here in town. The vibration joint... I dont know.