Hey Sean,
I agree to Martin @MVall and would add that it is always the best to buy the spindle cable ready-to-use with the spindle from spindle manufacturer. Reputable spindle manufacturers always offer this.
Another manufacturer that offers spindle/VFD kits ready to use is Mechatron (see here) (Unboxing video). There are many more spindle manufacturers but Mechatron is often mentioned because they also address consumers. They even have an ebay shop.