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's LTC3780 - High Efficiency, Synchronous, 4-Switch Buck-Boost Controller. It sells for about $20 to $25 USD.
My interest in this DC-DC switcher is to operate 19VDC Laptops and LCD TVs from 12V batteries.
I took the plunge and purchased two units.
You will notice there are three trimpots and an absence of documentation. Well that's not quite true, I did find the product datasheet if you can read Chinese.