Just following up on this thread as it might help someone with the same issue. Luckily there wasn't any play in the axle that I noticed. The seal I ended up getting was National #221922. It has an 8mm height instead of the 7mm original seal, but the housing is about 9mm so I figured it wouldn't hurt. As of now it seems to be doing the job. I'll provide an update if there are any issues in the near future.