Thanks everyone for the input. At this point it looks like the best solution is a DC to DC converter and a bridge and cap. There aren't many and they are a little pricey but this one looks like it will do the job: http://www.digikey.com/product-search/en?x=15&y=9&lang=en&site=us&KeyWords=102-1839-ND
It has an 18v to 72v range and is $19.95 q1.