Anybody Sell Transmission Parts ? - 904/999/A500 .063 Snap Ring

Looking for a flat .063 snap ring for the Forward Clutch, about 5.4" relaxed, 5.3" installed.
According to trans parts online, part # is 12878A, but transend says that # is for wavy. Neither place has it though and PATC doesn't even list it.
Other suggestions for sources?
I am working on a42RH, but the same number is listed for 904, 998, 999, & all A500.
For reference trans parts lists
12878A .063
12878B .075
12878C .081
12878W wavy

Thanks for any help or info you can add,
Rod