Apparently these components are getting quite nowadays. Even the cabler(s) I frequently use are no longer interested to restock the 4-pin and 5-pin DIN (half moon or 180-degree) connectors once their stock run out. They inform there is not much interest in such items nowadays.
Since I was in the Sim Lim area, decided to check out electronic part stores for the availability of the 4-pin and 5-pin DIN connectors (required by the Quads), as well as the availability of the female RCA connectors. As per informed by the cablers I frequent, these items are becoming rarer nowadays. Most shops do not stock them any longer. If you do locate stock, these tend to be the lower quality components eg discovered the DIN connectors with black plastic covers tend to disintegrate after some time. Hence I try to avoid these when possible.
Here's an example of the required cabling - my older cable.