Do you use all vex parts or a mix of others
A cheap option for me is Home Depot, Taps Plastic( i dont know if it is local or not but i get strong cheap plastic), and my local hobby store. Another vex compatible product is a bed liner for trucks the kind you can paint or spray on. I am going to use this Rhino Skin stuff and paint it on my tracks to give them more traction. It is a rubbery, rough, and tough textured stuff when it dries but you have to be careful not to get it in the links of the tracks, just on the flat side.