If you need something with a flange, ACE HARDWARE has nylon tube things with a flange on the end that would probably work very well. I've used stuff like that in custom stereo installations. I can't remember what the heck they are called, but they are a tube with a flange on the end, made in an amazing amount of diff. sizes. Hard Nylon. They will have them in their nut and bolt section with the other odd fasteners and stuff. Otherwise, the plastic tubing and a few nylon washers would be your cheapest bet. Less than $10 bux either way.