not many will do 1200 watts on 120 volts.
diy won't help if he has a 120 volt limit.
he has a few atx options that is about it.
Then you buy two PSUs and run one board each with them while still costing less than a bitmain and being way more reliable and able to keep up with the duty cycle of a 24/7 miners way better than an ATX psu.
You can buy HP/Dell/SuperMicro server PSUs that clock in around the 700-800w range for under $10 each if you do a bit of looking around. Throw in $10 in cables and you have MORE than enough power for an Avalon for under $40 total. The Dells you dont even need to solder, you can just use female spade connectors and glue them into place.
Pretty sure that still falls under the DIY criteria and meets the 120v limit while costing about a third of what you would pay for a bitmain or ATX psu. When ROI is a big concern with miners, I would think you would want to save money while increasing reliability whenever possible and this does both.