I agree with making them yourself... out of plastic or wood, your choice. if plastic, use either PVC, nylon, starboard or delrin, but NOT uhmw plastic, as it will check/crack over time in direct sunlight.
I would suggest that you cut the grooves you need first, then cut the piece to its finished dimension, as this allows for better control while cutting/dadoing the groove....
the teak slider tracks on our 34 were worn out, but rather than go thru the trouble to replace them with another set that may eventually wear out, with them still in place on the boat I used one of the vibrating cutoff saws like harbor freight sells, with a grout blade in it and removed even more material from the groove. then I built some inserts from "teflon impregnated nylon" with a groove that fit over the lip of the sliding hatch, then cut them down until they fit into the teak rails... so now I have a sliding hatch that moves as if its on bearings....