I'm not sure why anyone is still using this method. This thread was started before any connectors were available. Various threaded parts were found for the 801, 901 and 4081, but nothing was available for the 401 or 510, and this worked. It's a bit outdated now.
Most of the references to RCA connectors that you see are referring to making Warp's RCA adaptors which was started before one piece adaptors were available to make components interchangeable.
But if you really want to do it this way, I would check the Goodwill or other second hand shops where you can pick up the cables for less than a dollar.