I found a couple searching for "cdrom analog audio cable" on the famous auction site.

chrisNova777 wrote on 2020-11-03, 19:44:

then ir ealized theres also a number of CD-IN, AUX-IN, MODEM-IN audio connectors that i could be making use of either from seperate internal sound cards or external audio devices

I don't think internal sound cards generally have outputs that you could easily connect that way.

Yes they do it’s a standardized connection for audio from the 1990s

When nothing else works, dupont cables would do the job. 😉

chrisNova777 wrote on 2020-11-04, 12:31:

Yes they do it’s a standardized connection for audio from the 1990s

Yes, it's a standardized connection - but that doesn't mean you'll find it as an output on an internal sound card. I'm looking at the CT4830 I happen to have handy, and it has connectors for TAD, CD_IN, and AUX_IN, but there's no 4-pin output.

Jorpho wrote on 2020-11-04, 16:15:

chrisNova777 wrote on 2020-11-04, 12:31:

Yes they do it’s a standardized connection for audio from the 1990s

Yes, it's a standardized connection - but that doesn't mean you'll find it as an output on an internal sound card. I'm looking at the CT4830 I happen to have handy, and it has connectors for TAD, CD_IN, and AUX_IN, but there's no 4-pin output.

I have seen several soundcards that have unpopulated through-holes for 2.54mm headers in parallel with the rear jacks. As you say it's not a standard feature, but if OP is lucky it can be done.