I use a Lambda MiniPro Light Engine in a CNC123 bezel with 2 AA bodies & Kroll switch. It's versatile 'cos you can change the configuration to a 1x123 body & 1xAA body as well.
AA body with Kroll is on the right. Put two of those together, unscrew the tailcap from the 123 body, screw it to the bezel & screw in the 2AA body & Kroll & viola!
Another similarly versatile example would be an Arc LS with 2AA or 1x123 body.