Jaguar Getrag 265 4 speed gearbox

Hi Guys
I have a euro 1985 XJ-SC 3.6L 5spd that needs help with the gearbox. The internal plastic speedo gear stripped out when the transducer locked up. I located a replacement external drive gear but have had no luck sourcing the internal gear, or even a part number. I would even consider purchasing a replacement gearbox if necessary. Any suggestions or sources would be greatly appreciated