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).