If you want a Shimano cassette lockring tool let me know and it's yours.
It's the Cyclos double sided (Campag & Shimano) one with handle. The Campag side has started to burr so no use to me anymore, but the Shimano side has never been used so should be fine.
Not as good quality as a Park tool but has served me okay for 3 years, so even if you don't change your ratios should help you keep your sprockets nice and clean for a while.
[img]http://www.gbcycles.co.uk/PIX/MAIN/tocycl-m.jpg[/img]