Long ago, I lost the handlebar plugs on my bike. As a result, my bike is absolutely destroying the walls at work where I prop it up. Oops.
Fixed!
Writeup on the full design process using Fusion 360 and Fusion 360 Slicer can be found on GitHub, along with an SVG good for cutting the same out 3mm material (for a handler bar with an ID of 0.74" or so):