Yes, the USB units are awesome! I wired it directly to the main (RED) wire by the headlight and found a ground in the same area. I read 12.3 to 12.5 volts on the battery when off, and when running, it shows from 13.2 at idle to over 14 at higher RPM's. Here is one from Amazon:
https://www.amazon.com/dp/B07PDFJ966...roduct_details
A bonus with this unit is it also gives you the temp, (In Celsius though) and it also has an on/off switch so you don't have to turn on the key to check the voltage.
Edit: the unit that I pasted from Amazon is not the one I ordered, but when I clicked on it from my orders it shows this one. (without the temp gauge) They must be out of the kind I received.