Look it over real close and see if there is a bar code or part number tag on it.... When I needed to rebuild the transaxle in my L120 I found code on transaxle and it cross referenced to Tuff-Tork K-46...
If you can find part number on TA it make search easier...
Is it GX75 or GX275? There are plenty of trannies (used) listed on ebay. Try to bid for one. Or keep looking in Craigslist. Many tractors that are cannibalized for parts show up often.