If its a gear drive, the transmission is a Peerless. I forget the series. I have been looking for the same transmission for a Jacobsen Chief 1000 for several years.
Peerless was owned by Tecumseh. both have been sold twice in the last few years. I am not sure parts are still available. No help through Jacobsen either, at least the places I have checked. Jacobsen has been sold at least once as well.
Some parts still available through John Deere, I think. A version of that transmission was used in the 112 and 212. but not all shafts interchange. Jacobsen has the drive pulley on the other side, requiring different shafts than Deere.