Hello Mike,
I also purchased a? 301 without the cable (or power supply) in the past.
There used to be a guy on qth.com who sold power cables for various vintage (and not so vintage) radios. I haven't seen the posting from him recently though. A quick check just now, didn't reveal him either. Unusually, ebay also looks dry.. (not a member of qrz, so can't check them).
Last year I ran across someone at a hamfest selling NOS cinch jones 12-pin female (for the 301 and I <think> 101 line). I paid $10 ea. for just the connectors. I am planning on wiring up as needed. Given that it needs 12 ga wire, this assembly gets expensive fast. The connectors have cinch jones / patent molded on them, but the back-shell doesn't. I guess they could still be counterfeit. They do seem to fit snugly on the rig I tested it on and I plan on using as needed. Right now I share one power cable between 2 301's as needed.
I fear the cost of the connector and shipping alone would likely exceed $30 and that's without the cable itself - you would still have to supply wire and build it.
Best wishes locating one.
Jim
Mike Peace
Michael K.
Roland HB9GAA