Small, cheap power supply modules from Aliexpress
I have recently bought a BananaPi with the intent of making a automotive datalogger. I needed a simple power supply that would work reliably in my car. I found some nice looking modules in "The Thick Electronic" store on Aliexpress.
This shop has many different DC/DC modules that can be used in a car or boat - different voltages, step-up, step-down, larger and smaller power capacity and various connectors. Payment is covered by Alipay (basically you just need a regular Visa card to buy). Shipping takes about two weeks. I picked a small one encased in epoxy with a USB type A and micro USB B connectors (BananaPi uses micro USB B for power).
I used a stabilized 13.5V power supply as the source for the regulator under test, USB A-B cable and an electronic, controlled dummy load. The images were captured from a 150MHz oscilloscope (though cable inductance definitely smoothed out some of the noise).
3A full load
Definitely worth the price. Nothing fancy but just fine for powering digital gadgets.