Post #21 has some good info about using Power MOSFETs. I don't remember which one I used, I just had one in the parts bin that worked. Yes, I am using the stock switch to only turn on thr FET.
No pictures of the heat sink, it is a very simple "puck" with a raised area for the led to get proper focus. I don't think it will hold 3AA, it is only large enough for a single C cell.
**Edit** I did find several 3AA hosts on ebay. A little differelt style but were 51 led head.
Inspired by Aircraft800 and his Ebay mini aspherical, I decided to mod one as well. I got the cheap host from Ebay and then pondered what to do with it. As it turns out, the host will fit a 52 mm reflector and a C cell battery. It comes with a 51 led module and a 4 AAA carrier and a 4-way...