Groundsmaster 120

Hi to all. New to this forum. I did post a hello in the main home page new member thread. There I mentioned my current project which is a 1999 Toro Groundsmaster 120 model 30753 that I got off of a farm. It had been sitting for a couple years. One of the issues is the Peerless gearbox on the mower deck. The output shaft seal must be replaced. I'm trying to find a source for the seal. So far all parts suppliers on the internet list the seal as no longer available. No luck on Ebay or from Toro (website). I have a few more equipment dealers to try in my area. I'm still looking on craigslist. The seal part number from Toro is 788064. The gear box has these numbers on the tag in this order;
1100-010
Peerless
8266 0276
Any help you can provide will be appreciated.
Thanks, Ray