Dug this out of my box-o-stuff to replace the fork seals in my 81 900F. It is a 1 1/2" PVC pipe and has the inside edge of one end trimmed / chamfered to seat the seal without messing up the lip, and the other end is simply cut off to seat the bushing. Just slide and whack!! Works great on the 39mm forks. Got bigger forks then cut a slot lengthwise to allow the pipe to expand.
The chamfered end for the seal:
The square end for the bushing: