The CAD files for some custom plastic pulleys that we made are
here on our website. They are designed for use with pneumatic tubing bands but I would assume that you could use polycord as well if your team prefers that.
We found that this pulley assembly works well for picking up tubes, foam basketballs, and frisbees and can be about as versatile as you want it to be as long as you are willing to be a little creative with how you mount it.