Returning to this thread to report finding and successfully installing a replacement earpiece speaker on my Pixel 3 (not XL). Mine came from an Ebay seller in the UK called “fonejoy”. Shipping to the US was as much as the part itself ($12.64 part, $14.95 shipping) but it arrived promptly and seems to work.
https://www.ebay.com/itm/Official-Google-Pixel-3-Top-Speaker-G863-00072-01/333068348077?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649