904 Speedometer Cable Oil Seal

I just replaced the speedometer pinion seal on the 904 in my ‘65 Dart convertible. As I recall, the FSM tells you to put the seal on the cable housing, with the outer lip toward the pinion and push it into the pinion gear. That’s what I did, and mine quit leaking. I’d like to find a source for the seal too, in case I need one in the future. Fortunately, the rebuilt tranny I bought came with all the orings and the seal on a twist tie attached it.