Thanks for the comments guys!
FrogsInWinter, yeah I had to remove the upper window part of the original KL4-BK bezel. Unscrewing it is just a matter of turning the lens window anti-clockwise, the hardest part is just to muster enough strenth to unscrew it. I believe Surefire must have put some kind of glue on it to make doubly sure it doesn't unscrew. You guys might be stronger, but I found that using a heatgun to heat up the head and then unscrewing it was much easier.
KDOG3, did you order a new or old version of the KL1? I actually wanted to do this to my KL1-BK too (new version), but I don't think you can because the upper window portion is NOT removable. It is a one-piece assembly. Though I think you can do it with the old type as it is similar in construction to the KL4.
jlolson, I'm using the V21 nylon holster. The flap is just the right length even after adding on the strike bezel. I'm actually looking for the V25 but it's no where to be found locally and no one on BST seems to want to sell me one!! It goes without saying that none of the US dealers are willing to ship their products overseas