i actually just replaced the chain and sprockets on my 02 ST last week. went with 18T front and 43T rear and used the DID 530 Xring chain (believe it's p/n 530VM for an OEM replacement). there is a posting on this forum from 6/28/06 with questions like yours "aftermarket chain question".
i ended up using a standard 108 link chain (530 size) from
www.accwhse.com. this chain is riveted, not the clip-style master link. ended up having a dealer rivet the chain because i was not comfortable i did it well enough without the proper tool.
if i had to do it again, i'd buy the proper tool, even though it's ~$100, for installing the masterlink and take maybe one link out - as it is all the adjustment for taking slack out at the rear wheel is used up and the chain is just at the proper tension.
good luck.