There are plenty of other options available to you - you should be able to pick up something appropriate from an electronic surplus store. First - you need to determine how much power (in Watts) you will need to run your radio gear. Then - try a Google search for "DC-DC Converter 12 24" (or 12 to 28V) - and look for a model that converts 12V to 24V or 28V, and has at least as high a wattage rating as the equipment you are running. If you are unsuccessful in your search, you might consider using a lower-power DC-DC converter just to charge up an additional battery in series, and make your own mini-24V system on your Mule. Most radio operations are intermittant - so you may not need to provide the full output power needed by the radio directly from the converter.