I bought all the cable parts I needed from Amazon, wasn't expensive. Digikey has them too.
I believe PC Components was the Amazon store that had them. I bought the bulk 25 piece kits because I was doing it for a several computers, didn't buy the crimping tool because I have a nice bench vice and just do that real carefully. Heck back in the day I used a hammer or channel lock pliers.
The nice thing about making your own, you can pick your own lengths and spacing just keep it under about 10 feet total, I keep them under 6 feet but the spec sheets claim 10. Each connector says pin 1, keep that on the same side of the cable and the same face. !____!__! you're good to go.