I think I have it now. The new mounting lug is done and I had to make new brackets for the top sided lug, but it actually looks like a better position than I had it in before- less in the way now. Here`s how I did it:
Drilled and tapped the 4mm threads that the Magic Screw on the bottom goes into so that there`s a threaded hole all the way through the heat sink. Fabbed a small aluminum block with a mounting hole for 6mm bolt through the side and a seriously counterbored hole from top to bottom for a 4mm button head screw. That screw shared the same hole as the Magic Screw. Filed more heat sink and filed the bottom of the aluminum block so they match up (I didn`t do a very good job of that part, but it`ll work). Screwed the block to the heatsink and tapped a 3mm hole through the sink and into the block, put in a little screw from the inside. Took the block off again and pared down the excess material. Put it all back together with Loctite and work out the mounting. Done. Looks pretty good, eh? I just need to unwire the spare light, wire in the repaired one, and we`ll see how it lasts this time. Third time`s the charm!