I found some on EBay that are a rubber type, lubricate with oil or gear oil and can be used over according to the literature enclosed with the gaskets. The name of the company is Vintage Gearbox Inc.
I believe the company is located in California, maybe $25 or so plus shipping. I am using them on my '38 half ton pickup. Seems that the leak I get is coming from the threads of the screw collar, I think the gear oil leaks back through those threads so my next move is to use a sealant that is "gear oil resistant" and put it around the edge of the collar and the tube, comes in a gray color.
Later,
Glen
1938 half ton pickup
