The eBay connector came with short leads installed, but I pulled them out and slipped in the spade connectors already on the alternator harness wires:
The connectors on the short leads each had a tang that clipped them into the shell, but the ones on the harness did not, so to keep them from backing out when the plug was inserted, I potted them in with RTV:
When the harness is installed, at idle the battery is charging and the Christmas lights are still gone: