5050 parts are normally readily available on eBay, 5050 being one of the R2Rs that remained in production till late 90s IIRC and sold in 100s of 1000s and Otari made the parts available for long after that.
Last option - since it's also easy to get to Otari specs and manual, trf can be wound to spec from scratch.
Top class machine, wish you the best of luck getting it back to use!
