https://nl.banggood.com/DP50V15A-DPS...r_warehouse=CN
This is a complete adjustable power supply which can take about 60v. There are many versions based on the current rate, the 5015 can handke 15A. There are also nice cases to be found.
Also there are plenty of DC-DC converters to be found, search on ebay/aliexpress/banggood/wish/etc to "dc dc converter" and look at the specs.