In any case getting a complete AC adapter for 5$ or 6$ seems to be not possible and the next price points are in the 40$ US plus zone.
However if you happen to already have a good DC power source of about 20V to 45V you can use this
https://www.ebay.ca/itm/5V-And-12V-Regu ... Sw5T9eAyS2
I found that I already had one of these in my stuff and it works great, and with those terminals it's much easier to hook up.
The price really seems great.
