If you're going to a machine shop may as well just have the tool made. It's a pretty quick and quite easy job and aluminum would be just fine.
I don't think any of the rubber ideas are that good, may help some, but an accurately turned metal guide will be far superior.
I forget the installation tolerances for rubber lip seals, but thinking they are much less than you'd guess. And I'm sure for a long seal life no run-out is best.
Grigg
