I know several have tried the neat little DC-DC adjustable power supply modules you can get from China - eBay... I just got a new one. The price was low (aren't they all) and this had what appeared to be a bright clear LCD screen with nice up/down buttons to adjust and it also monitors current. Good for a 20 V power input (laptop supply!!) and up to 3 amps but they recommend 2.
It is small - tiny actually. Comes with a tabbed little plexi shield "box" and two little red plexi button extenders, plus two screw to hold it together.
I've attached a photo so you can see. To give you an idea of size I left the ferrite on the end of the laptop power supply cord in the photo when I cropped it.