[skidlids]

The S4 coils are very similar to those found on R6 Yamahas and various other Japanese bikes from about 1998 onwards.
I have picked up a couple of sets from breakers and auto jumbles for as little as £10 a set of four.
They vary in lenghth a bit depending on which model they were meant for, may be worth looking into. they all use the same connector from what I have seen which is a 2 pin jobbie and different to the coils and connectors found on 749/999s