Not cheap for a new one (and seems outof stock - so maybe not available) and both have plenty of life in them - unsure why the generator teeth are off, misalignment maybe ?
Can I simply build up the broken tooth (one tooth on one, three on the other) with my Mig (with stainless wire - bit harder) and then reshape with my lathe and a file ?
Failing that - there must be UK companies which rebuild unobtainium sprockets
Both were excellently done jobs and reasonably priced. May be worth a ring to establish turnaround times.