Stereo Level to Mic Level Attenuator / Cable

I’m currently trying to find a cable that would be able to feed the audio of an intercom to my iPhone’s mic or vice versa (thinking of TRS male to TRS male, but any is fine).

I’m looking for a cable to take the headphone audio of a general device, and bring that audio down to the mic level of an iPhone. I would like to record the audio of that general device with no issues (in my case, it’s a motorcycle intercom).

I saw that headset buddy has something similar, but it’s a TRRS to TRS, don’t think it would work in my case https://xender.vip/ . I’ve also seen other cables that could do something, but it’s specific for cameras. So far, no luck, would like a product recommendation. I’m looking for a product recommendation that could do exactly mentioned above.