Engine/Transmission (1998.5 - 2002) transmission rear seal

[highgear]

1 have a problem finding a trans rear seal for my 1999 3500 5 speed 4 wheel drive. i have tried carquest napa and schucks. do i have to go to the dodge dealer . it is 100 miles from me. the seal i got from carquest looked o k but was 3/8" or so smaller than what i think the seal in the rear of the transfer shaft is any ideas thanks .