What wire or cabling

What wire or cabling is everyone using for the connections to the motors. I need no more than 18ga wire for my motors but am finding it difficult to find 18-3 S.O. cable. Thats 3 and a ground. This is used most times as I can see as extension cable or easy pull cable in factories. But they mostly use 16ga. The reason I want S.O. is for is't being very flexible.

Thanks
Steve