If you need plenty of current at “extra-low voltage” levels, the cheapest way to get there usually is a decommissioned PC PSU. An ATX power supply just needs some “dummy load” at each rail to start up properly (as it has not been designed for really low loads).
The first PSU I modified was used to power some Peltier elements, becuse I wanted to quickly cool my beer at one or two open air festivals. The PSU was used for tests in the living room, the cold box had problems with thermal resistance between Peltier elements and beer, but in the end it could at least power a standard car cooler when we got our last fridge and had to defrost the old one a day before.
Here I replaced the +5V, +12V and GND-wires and tied the rest together on the inside.
This is the “dummy load”: a fairly large resistor on a “fireproof substrate”.
At work I had a temporary problem with the calibraion of my “proper” bench top power supplies: every two years they were gone for a few weeks. Simultaneously.
This was my workaround: an “adaptor” from ATX-connector to banana jack.
The solder mask is spared on some traces, so a wire can be added.
The dummy load consists not only of power resistors, but also an incandescent light bulb (radiates the heat away instead of getting hot iteself exclusively) and a relay.
Additionally there is a USB connector on the 5V rail with a jumper, so you can charge your phone (or power bank) while working with this.
No case has been built yet. This is still just the workaround.
…and quite useful until my first 3D-printer got his own dedicated power supply. 😉
When my brother discarded the next PSU, I knew what to do.
Dummy load is internal this time.