If you have soldering skills, you can probably mod them yourself. It will be a bit annoying since they likely used enamel wire, which can be fun to get cleaned enough to solder again. I do not know for sure what pin-out they are using in that harness, but it can likely be reduced to 3 or 4 pins from 5 so you can use normal 1/8 or 1/4 TRS or TRRS connectors.
My approach was to make our own headsets from "scratch", along with a custom car harness. I bought pre-molded radio side connectors that have the dual pin connector and then go to pigtails, and then I bought a bunch of 4 conductor wire, speakers, mics, and TRRS connectors. I can look up the exact parts at some point.
If you're not handy with soldering and wiring then honestly just buy new headsets. Poorly made DIY versions fall apart fast when abused in race cars. Look for ones that don't use IMSA connectors, those are expensive for silly reasons (the actual connectors are just expensive). Instead look for ones labeled as NASCAR connectors, or just normal headphone connectors. The larger NASCAR (1/4") connectors are easier to manage with gloves on compared to smaller 1/8" (3.5mm) headphone connectors however.
Edit, just to dump the part since these aren't always the easiest to search for, this is the radio side connector I used. I personally hate the coiled stretch section, so I cut that section off and just wire them up to new sections of molded 4 conductor.
https://www.ebay.com/itm/233643435113
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