Looking for single mode buck 3A driver with pot for dimming

Having a hard time finding a single mode 3A constant current buck with provision to add a pot to it. Must take 7 to 18 VDC in. I need something cheap and reliable.
Cheap in the 5 to 15 $ range.

I'm in the same shoes as you are, except I'm willing to pay up to $50 for one

I modified a dealextreme driver (20330) to use a 555 ic for variable brightness with a pot. The driver can be modded to run at 3amps by changing the sense resistor. The driver can except higher voltages if some componets are replaced. I never got around to modding for higher voltage but pretty sure it can be done. Here is the thread for the pot and 3 amp mod. Go easy on me was the first post I ever made. At DX forums member says to replace C1 capacitor with a 10uf capacitor rated at 16v or higher to work up to 16v thread here. Read the entire thread he gives the wrong rating in his first post. There has also been others at DX to do this but I have not tested it past the normal 8.4v in.

Shark Buck 3A, $25. Has an on-board trim pot. IIRC, that trim pot is rated for some limited number of turns (200?). If you want to use a pot as your user interface for infinite brightness adjustment, then you want to replace the on-board pot with an external, logarithmic pot, such as the Panasonic 20K logarithmic potentiometer (Panasonic part # EVU-E3JFK4D24).

TaskLED has the H6CC and H6Flex that would fit what you are looking for. A little pricey though.