Trying to fix a BSA Cadet (major??) for a friend. Not sure what the part is called though? It is a bar with a notch at one end where the trigger sear engages, and a threaded part at the other which screws into the the main piston cup. It has sheared about hlf way along the threaded part sadly. Anyone got one, know its proper name, or where I can get one please? Thanks, Mick.