Left earbud IR cover came out and broke

Sony support sent me to their only repair center. They quoted $40 to update firmware and sync the 2 earbuds, and I have to buy a new left earbud entirely for $100. That is ridiculous, and I was wondering what material I could potentially buy to replace the part that came out, or should I ignore it? The oval piece fell out and snapped off about 2-3mm of one of the rounded edges, The seal also came out, currently just have it wedged the wrong way in but I believe the IP rating has been reduced.