SJS Cycles also do new 7,8,9 and 10 speed thumb shifters: http://www.sjscycles.co.uk/gear-shifters-rapidfire-trigger-dept372_pg1/, bit pricey though.
On my newer 27 speed bike with XT front and rear mechs and rapidfire shifters, I could never get it set up so that the front derailleur cage wouldn't rub on the chain. In the end I gave up and fitted a friction thumb shifter that I could "trim": http://www.sjscycles.co.uk/sunrace-thumbshifter-left-hand-prod23293/, it's really cheap and nasty looking, but works perfectly and is lighter than the XT rapidfire it replaced.
On my newer 27 speed bike with XT front and rear mechs and rapidfire shifters, I could never get it set up so that the front derailleur cage wouldn't rub on the chain. In the end I gave up and fitted a friction thumb shifter that I could "trim": http://www.sjscycles.co.uk/sunrace-thumbshifter-left-hand-prod23293/, it's really cheap and nasty looking, but works perfectly and is lighter than the XT rapidfire it replaced.