[CMOTD]

I am no electrician either but slot cars run at 12v with a current draw of 1-2 amps max so virtually any 3 core flex will do the job. 0.75 mm² will cope with 6 amps at 240v. Your local diy place should have something suitable but Amazon LINK will cut to length if all else fails. Truspeed supply cables for their own controllers so they will fit as well. LINK. There is no such thing as cable specifically for hand controllers.