I am rebuilding a 1938 German Adler bicycle, with a 3-speed gearbox in the the bottom bracket and need to replace 3 fossilized rubber oil seals. I can't just go up to a parts counter and ask for Adler Par numbers F 625 E, F 625 F, and F 625 D. Random web searches and McMaster Carr are turning up some seals that are close, but not exact for some and absolutely nothing close for others. There are a lot of reproduction car and motorcycle seals, but they are all listed by application, not dimensions. Does anyone have suggestions on how I should be searching for these? I tried soaking them in oil of wintergreen and alcohol which softened them up temporarily, but are rock hard again a few weeks later. I could probably get away with cutting my own out of sheet rubber for some and replacing one with a rope oil seal, but I'd rather get closer to the original. I'll be running 00 grease in the gearbox so leakage should not be too bad. Thanks in advance!