DC1428A, Aircraft Spruce Part Number 11-11685, is a 14V to 28V DC-DC
Converter for use in home-built aircraft. This unit provides up to 3.7A of
28V power to avionic systems in aircraft that have 14VDC electrical systems.
http://search.ebay.com/12v-to-24v-co...fsopZ1QQsojsZ0

2 more days on auction or for sale.