After looking at Zeal's cables, I wanted to get one!
The main issue is that I own 2 filco tkl and their cables are not detachable. That's why I wanted to mod one!
I used an old micro usb extension I had.
I soldered the cables from the connector to the original cables and then taped them. I also cut the case to make some room for the connector:
The result:
At first I wanted to put the connector on the side but I couldn't put it that way because of the pcb.