I hate to say it because I really hate them, their ethics and ludicrous demands, but if people are concerned about image theft then a company called Pixsy offer a monitoring service to notify you if your images end up elsewhere. The first 500 images are free but payable after that.
Once you are notified then you can give Pixsy permission to pursue those individuals to stump up cash for the infringement. They make their money in recovering fees for copyright breaches for a high commission rate of something like 50% of the recovery. Success rate is pretty terrible from what I know in Europe (except for the very low hanging fruit) but may be better in other countries.
Try posting in the comment section of the model saying that you’re the owner of the model and you didn’t allow him to sell. That’s what I did and he immediately took down the listing.
I reported several models from that same user. Creality Cloud removed the models from that user’s page, but they still show up in search, and the models are still available.
I have no interest in contacting thieves to tell them to stop thieving. The platforms need to know about this so they can ban them.
