You can just trim the wires from your current lead or buy a replacement.
Ok, so I went back and double checked, glad I did, it is not the XH2.54 I thought it was, but is in fact a JST PHR-5 (search for that and look for a 5pin). You can get bare ones all over, but getting a pre-made lead will probably mean ordering from China off Ebay and you are not likely to find one with a USB connector already attached so your only option is to buy one from Pexon or build it yourself, which again, is not a bad thing.
As for how to wire it, USB is pretty simple with only 4 wires inside, plus an optional shielding wire (which Filco uses).
In a 4 wire setup, the two outermost are red and black, these are your power, the two inside are often white, yellow or green and these are the signal wires. The 5th wire is connected to shielding and the USB plug itself, if it has any (cheap ones do not), this can also be connected to black/ground when adapting a 4wire to a 5 wire or simply ignored (note, some devices require it to work). If you swap the power wires, most devices will simply shut down and the USB port will stop working until yo reset the hub or the computer. If you swap signal wires, you may or may not get a connection to the device, most often you get a failure to find the device driver (some can work in reverse). It's pretty simple and you are more likely to burn yourself with the soldering iron than you are to damage your keyboard. You can find soldering irons at dollar stores for under $5, they are terrible, but for a small job like this it will work just fine. Don't forget heat shrink, some electrical tape and solder. I HIGHLY recommend leaded to start with, but wash your hands after. You can use heat from the soldering iron or a cigarette lighter (use the blue part of the flame not yellow) to shrink the heat shrink tubing. Lastly, make sure no exposed metal is showing which can contact a pin on your keyboard.
If you look at the Pexon cable below, you can see the red and black power and ground (red and black) and in this case white and green signal wires. The orange wire is the shielding and is covered by some tubing. Most people just twist the strands together and solder them to the wire and cover in heat shrink or electrical tape.
Show Image
(https://cdn.shopify.com/s/files/1/0651/0379/products/MG_5855_720x.jpg?v=1494797587)
thank you so much im decided to try to do it my self since i really want to build a micro pad in the future