This is my original wire holder, but with the ability to hold more than one wire.

It's a bit expensive to compute, so preview won't work in the customizer, but two of the STLs attached here are from Customizer, so it does work.

It does benefit from a bit of support since there's a hard overhang. It's possible to make that unnecessary, but I don't mind it for this.

Mounting

You can add a mount plate and screw it down, or you can just do what I do and tape it to a surface with Scotch VHB double sided tape.