You might try looking through some Force or Chrysler parts books? I’ve found a few impellers for West bend’s that way, some of which are still available from Mercury. Stainless steel is the best, but a regular seal would work… maybe if coated in perfect seal or with red loctite. How about a picture of your motor? I’ve always wanted a larger HP West bend… Their something different and have tons of power!
If you can find a part number on the seal, try Ebay. I needed some bearings for an Oliver motor a couple years back…nobady had a clue where to find them. I did a search with the bearings manufacturer and # and found several of them for 5 bucks a piece, new old stock in the box. Couldn’t believe it!