Here's a link to a OSHPark project to buy constant current LED control board: Passenger Car Lighting Board on OSHPark.
This small board supplies flicker-free operation with adjustable intensity and DCS protection. Build cost is around $2/ea, maybe less with off-shore components. This is based directly on my commercial LED Lighting Regulator and has the same functionality. Many people have built these and are using them. If you're looking for a quantity more than a handful, going off-shore to one of the many PCB houses would probably be warranted to keep the costs down.