7 1/4 Rearend Axle Shaft Seals?

Hi, I wanted to know about parts and replacing the axle shaft seals on a 7 1/4 rear. I seem to have gear oil leaking down the metal cover (held in place with 4 nuts) at the backing plate. Is there a seal in there at the outside end of the axle tube and where would you suggest purchasing these seals/parts. Any help would be appriaciated.