The front axle vacuum motor should be available from rock auto/bjsoffroad/jeep4x4center, I think, it depends on the axle. However the transfer case one is not. At least it was not for my 1983 with a 229. I was able to get mine working again, fortunately the diaphragm was still in good condition.
I did not finish my investigation of the front axle, do to work related things but that one should be findable. There is also a very expensive manual kit for the front axle.
1983 Jeep Cherokee Pioneer (bone stock)
IL6 4.2l, AC, auto, and 1 fashion visor
front axle 40170 model # & looks like a Dana 44 w/ 3.31 gears
rear axle AMC/JEEP 20
transfer case 229 AM
auto tranny 909 I think