I checked Rakuten but they don't seem to carry watch parts, just watches (and a very limited range at that). I googled "Casio watch parts" and was directed to Casio USA's support page for purchasing parts but was shown the below message. Think they just want consumers to get parts through their proper channels i.e. depending on your country of residence. May just live with it unless it starts peeling. But I'm quite curious as I've seen the bezel being replaced on Youtube videos and it seems like it can be done in a jiffy by anyone at home. The bezel seems to be a standard shaped shell with just different colors/markings for different models, and it certainly doesn't look that expensive lol!
Service Bulletin for Casio Watches:*
The spare parts including bezels and dials of some Casio watch models (click here for complete listing) will no longer be sold directly to our customers. If you have one of these models and it requires service, please contact Casio Support at 1-800-706-2534 Option #2 and we will provide you with a shipping label to ship your watch to Casio Factory Service Center to be repaired. Please note that repair of your products is subject to Casio's Limited Timepiece Warranty Policy.
*This information may be subject to change without prior notice.