Search for a small DC-DC converter

[extragoode]

I got 20 watt 1000 lumen LED that's going to replace my headlight on the nerdcycle. It's only about the size of a quarter, but requires a heatsink. I'm not sure how big that needs to be. The big problem is that this LED isn't very bright at 14V. It's made to run at 18V and 1.1A for full brightness and works wonderfully when connected to a drill battery I've got that's charged somewhere between 17.4V and 19.2V. So, I was wondering what's the best way to get a voltage and amperage that high into the headlight assembly. A small simple commercially available transformer would be ideal if it isn't too expensive, but I'm not opposed to building electronics from scratch if it's required to fit the size, space, voltage, amperage, and cost requirements. What are you guys' suggestions?