2-stroke - the SS doesn't need fitting while the clutch is out. Can be done anytime, unless you mean you'll get someone to do it for you?
Can try ESP Engineering, they have a GB going on SRS Forum. Can try QST as mentioned, or AMD. Could try the one advertised on EBAY for £30, which is apparently ok. Can try the JHM one which gets rave reviews, but doubt you'd get it in time. The other one is an AWE one...
Personally, I'd be going for an ESP one, coupled with a weighted gear knob, which makes the gear movement alot more precise. Perhaps also couled with a DTS or Gearbox brace to tie it all together. That's the recommeneded mod if going for a SS...
PM me for any further info !!