Support disc for chain-driven reprap Z-axis

I use bike chain for the axes of my reprap, and need to have a way to keep the chain staying on the jockey wheels of the Z-axis. This is only a problem for the Z-axis because the chain is horizontal and tries to fall off. For now I'm using polymorph rings (shown in picture), but wanted to make them look cooler. I haven't printed these yet, but the plan is that two of these can clip together and won't necessitate rebuilding anything. There's some terrible openscad code that makes the tab 0.95 tim