Chris aka Dubesinhower recently posted a video highlighting replacement controller cables from JT Studios and Retro Game Restore. These are meant to be high quality replacements, for people looking to repair their original controllers, or build new ones with a braided-style cable. The NES cables are sold in single packs for $12 and the Famicom ones come in a pair for $18. Check out the video above for installation instructions:
NES Cable (Single): https://jt-studios.com/product/nes-controller-braided-cable/
Famicom Cable (Set): https://jt-studios.com/product/famicom-controller-braided-cable/
A few notes. First, remember that the original consoles (and controllers) are over thirty years old, so you’ll want to approach the install with caution. Set your desoldering iron to a lower heat at first to start (maybe 350f?) and when in doubt, just take it slow; Feel free to use flux and even add a bit of fresh solder to the original wires, to loosen up the connections before uninstalling the original.
Also, I 100% agree with Dubes’ opinion on the price: If you’re on a budget, you can easily get replacement cables for far less on Aliexpress…but as always, you get what you pay for. There’s basically zero quality control on a $2 cable, so it may be fine, or there may be fit issues with the NES controller port, or just overall poor quality.
One last thing: The Famicom cable I sent Dubes was a pre-production prototype, so the colors and pinout of the one in this video might not be the same as the production versions. Just follow the instructions on the box and your install should be fine.