$20 Bluetooth headphones on Amazon - What could go wrong?!
This is a replacement for the rubberized button cover that eventually peeled off of my set of TaoTronics TT-BH027 earbuds. I printed them on a Form 2 to ensure high resolution and fit. You loose the water resistance that the original cover had, but you regain buttons - so I see this as a total win.
Keep the supports on the outside. Sanding the inside will be nearly impossible or at least super frustrating.