This is a pretty common topic in any bike forum.
Bike manufacturers generally buy in ancillary components; things like brakes, suspension, electrics, pumps, taps, caps, etc etc. So often the same component will appear on radically different bikes and different components will fit to the same bike. I think Suzuki probably fitted a fancy 6 pot caliper to a set of fairly standard forks which would fit standard 4 pot calipers.
I used to work in the bike trade, we had catalogues of components which listed cross references. I'm sure, with a bit of hunting around, you can find catalogues on the web which list 'part numbers'. If you want a brake lever; look up the relevant Triumph lever and see if any other bikes have the same lever. This only works for pattern parts though, I dont know of any genuine part cross reference, though they must exist.
Try
Staniforths:
http://www.staniforths.com/stan_catalogue.htm
(Triumph brake levers are all the same and common to most ZX/ZXR kwaks)
Feridax, Tran-am, fowlers, B&C express and Bickers were other ones which are used in the trade. They're a very private bunch and most of the websites are useless.
I used to have a wonderful Tran-Am catalogue around which listed all sorts of stuff. I've never been able to work out what fuel tap triumph use though; I know it's common to some Yams and Kwaks...