I have the afedri sdr-net revision 3 sdr. You have 1 of 2 ways to power it.
2-Dedicated power supply
I did not want to run 10-15ft usb cable to my laptop so I choose option 2.
Here are the specs from the latest afedri manual. I went with a Jameco power supply. The part number is 1953647
You can order directly from Jameco. It is a perfect match for the afedri-sdr.
If you want something other then what Jemeco has to offer then look for a DC regulated linear power supply rated at 9v 500mah tip + sleeve -.