Welcome, I don't have any drawings for a positioner but I have made several in the past. Just use your imagination and start with a supply house cataloge such as Graingers. All you need is an AC/DC gearmotor and speed controler. A couple pillow blocks and cold rolled round stock for the shafts (1"), some # 35 chain and sprockets. Some channel for a set of pipe rollers or some square tube or angle for a table top positioner. Jetline uses a piece of 10 or 12" square tube for their housing, everything is inside and protected from sparks. Don't forget to design in some safety guards as well.

Plan on spending around $300. Look at manufactures such as Atlas for basic design ideas.