AFAIK custom cable makers can use any connector that the customer desires, so they certainly can use similar connectors. The 99's aren't the only headphones with recessed connectors, and the plug itself is merely a 3.5mm TS. Here's an example of compatible connectors :
https://www.ebay.com/i/113871193058?chn=ps
EQing them to our liking would make more sense than replacing the cable IMHO. It's cheaper, and at least we know what we're doing.
That can be due to silver oxydation, IF you have silver connectors. In that case you need to clean them periodically with a special cloth such as the one Audioquest provides with their headphones. That suppresses the strange sounds.