Prevalent on ebay and Amazon is the "LTC3780 Automatic lifting pressure Constant voltage step up step down 10A 130W" DC to DC Converter.
I'm not quite sure what the "Automatic lifting pressure" is about, but it is a fairly well designed DC-DC Switcher based on Linear Technology's LTC3780 - High Efficiency, Synchronous, 4-Switch Buck-Boost Controller for about $20 to $25 USD.