timmmay (or anyone else)... during your research, have you come across any DC-DC chargers/UPS units which can operate with only 12V input?

My ONTs are both on my main UPS, but I have a remote low power system I need to power independently, and I am unable to change the 12V power supply (built in to a cabinet) to the higher voltage required by most of these units. The cheap units also only pass through the (higher) supply voltage, unless it drops below a minimum, and switches to battery. To use such a thing would require a boost in voltage, then a drop in voltage, all of which can be done for less than $10 in parts, but it's a messy solution.

The OpenUPS units from Mini-box.com are about the only thing I've found which can do what I want in a single unit, but they are expensive ($US119) compared to under $US30 for the basic units.