Goomico, 1st, what year is your bike? 2nd, are you aware that the seals are directional?
The tool only works with earlier model airheads. If the seal is resting against a metal ring (top) then the tool would not be of any use. However, if you want to try to make your own tool, just get a short piece of PVC pipe with the ID of the pipe slightly bigger than the push rod tube. Cut the pipe in half and then cut the angle in to match the top surface of the seal. I'll add a picture of Graham's (not pretty, but functional) in a little bit. We both have leaky push rod seals and have just been living with them for a couple of years. It's on our "to do" list. We just clean them up and keep riding.

If you have a Haynes Manual (R50, 60, 75, 80, 90 & 100 Twins), check out page 36 for a picture and dimensions of the shop tool.