If you work security, you may not want the McClicky. There are reasons Surefire designed the original tailcap to be a momentary push button, so that the light could be turned off as fast it could turn on. Your call.
Another reliable source for LED drop-ins is Lumens Factory. They make a very nice XP-G R5 drop in in either Neutral White or 90+ CRI, in either single tactical mode or triple 5%/30%/100% mode, with an output of around 350 lumens. I have one in my G2 along with an eFest 16650 rechargeable. Works great, lasts long time. As long as you don't run at full power for ten minutes or more at a time, you won't have a heat problem.
My first good light was a G2, and I was lucky enough to find another original G2 on eBay recently. The LF drop in and the eFest 16650 make a good combination while leaving the G2 as essentially stock (I still have the P60 and a couple of CR123s if I want to return to full stock). Enjoy yours.