Mini DC-DC Converter Adjustable Step Down Module Input DC 4.5-24V Out 12 9 5 3V3 2V5 1V8

Adjustable output, requires soldering a tiny bridge, very tiny indeed! 

Output slection 12 V 9 V 5 V 3V3 2V5 1V8

97.5 % efficient.

Rated at 3 amps, but I wouldkeep it under 2 amps without lots of cooling.