I might suggest using things called Wellnuts - rubber T shaped piece with a metal threaded nut in the stem end. The come in various sizes, you'll probably have to use a larger diameter size to get the length you need.
You would have to drill the plastic parts to get the holes big enough. Then you put the whole thing through both holes like the expander things, put a machine screw through, tighten it up and the screw pulls the rubber shorter and expands it tightly in both holes. Works the other way to take it out - completely re-usable. Most good hardware stores carry them in the nut and bolt section. Relatively cheap.
You would have to drill the plastic parts to get the holes big enough. Then you put the whole thing through both holes like the expander things, put a machine screw through, tighten it up and the screw pulls the rubber shorter and expands it tightly in both holes. Works the other way to take it out - completely re-usable. Most good hardware stores carry them in the nut and bolt section. Relatively cheap.