Pulleys for photographic slider

Hi, I am trying to locate certain parts that I would like to attach to a photographic slider. Some of these parts a ready available from specialist photographic dealers but too expensive for me. I would like to add a compact DC motor with a pulley system that will pull the sliding platform that will have a Canon EOS 7DMK2 mounted. I have the slider, the 12VDC motor, 12VDC variable controller. I need to find a way to mount some slider pulleys that can be mounted to the side of the slider which is connected to a belt. I have seen a picture of a pulley but am unable to locate where this is from that can be mounted onto a plate as a guide for the belt to the motor. I will try to get some pics of this but not may are shown.