Not aware of any complete commercial product, I think you would have to do some building. There are a lot of small switching DC-DC voltage converter modules available in the Electronics world if you have a sufficient level of electrical knowledge.

If interested, try www.newark.com, search for DC-DC converters. There are a lot of ones available, with data sheets (under tech info) that will show what is needed for building a system, again if you have some knowledge. Use the search fields to narrow down the list, might take a few tries.

Suggest you start with at least double the current that you think you need for a robust build.