ebay have them going from time to time,
luckily it's one of the more common things going,
a place in the uk (newcastle under lyme, i think it's D&K motorcycles) are breaking one at the moment.
all depends on model ie pre 95 VV have two cam sensors, some have no variable cams some do ( VV ~ variable valve)
there's schematics for them on here . . . .
http://forums.banditalley.net/index.php?action=tpmod;dl=cat2;tpstart=0have fun
(search under GSF400, GSF 400, Bandit 400, Bandit400 or anythinm else you may think helps like the gk75a etc)