I don't think I've ever been as cross with Apple as I have over this silly little $5 part. I managed to lose an ear tip (perhaps because it wasn't fitted securely) on the day I bought by AirPods Pro... but simply cannot get a replacement.
The online support system has an option, but in the UK this just leads to a dead end where it offers whole replacements not the ear tips despite the latter appearing on a previous screen (see screenshot).
I spend 45 minutes on hold at various places around the Apple support line (plus a further 30 minutes on an earlier occasion when I gave up). They said it was a sales not support item (despite it being listed as support not sales on the website); they said I should drive to an Apple store (3-4 hours return trip, and the two I have tried said there was no availability anyway).
Aaaargh.