Side note: Where do you North American chaps buy your (low volume) components from? In the UK we have RS, Mouser, Digikey (ships here pretty easily), Rapid, Farnel etc. Whats the most prominent in the US?
Depending on his needs, these small modules from China are tough to beat. They are available in a wide range of maximum voltage and current capacities. You supply DC power at a greater voltage than you need and these modules supply easily adjustable voltage or constant current, adjustable to several decimal places.
You can limit max voltage, current or power. You just dial in the parameters you want. Cases are available separately that include a coolimg fan.
[Urlhttps://m.ebay.com/itm/Programmable-Constant-Volt-Current-Step-down-Power-Supply-Module-DC-50V-5A-E0W4-/351824924923?nav=SEARCH]Here is a link to one unit[/url] but search a bit to find the wide range available.