For Apple Watch Series 4 Series 5 40mm 44mm Bezel Frame Housing Crown Screw Button Nut Cover
Replacement For Apple Watch Series 4 Series 5 40mm 44mm Bezel Frame Housing Crown Screw Button Nut Cover
Apple Watch Series 3, watchOS 7
I'm sure you would have to contact Apple Support to see if they would sell you the part. My guess is you would have to have Apple repair it.