I have an extra Nintendo Classic pinout edge connector-style harness available. $35 shipped.
Works for DK/DKJR/DK3/Popeye/Mario Bros. Should be plug and play with your existing cabinet, given that you have video and audio cables, coin door trimmings (in the DK small connector style), and a PP-7B power supply. Some VS setups (I think only dedicated) use the later molex-style coin door connections and different PSU. If yours was a Unisystem conversion, I believe you're all set with one of these. See pics.