If you have the RRT-21, you probably know Jetbeam has a RRT-0 which is similar to Sunwayman's V10R. Also, if you don't want to spend $150, buy the non-ti version of the V10R along with the V10R AA extender, by all accounts they fit together just like with the V10R Ti (I've got a V10R anniversary edition and the Ti AA extender, so I'll be able to confirm or deny that in a while). Granted, not as fancy looking, but cheaper.
I'd agree with not putting a light like this on a keychain. If you're looking for a bright keychain light, this is the AAA that I'm waiting for:
http://www.candlepowerforums.com/vb...umen-AAA-Flashlight-(photos)-Work-In-Progress