Replicas like counterfeits and fakes are not allowed on eBay. Although many may be listing them, I hardly think it would be wort the risk of getting your account locked up by eBay once your reported/caught.
This what eBay has to say -
We don't allow replicas, counterfeit items, or unauthorized copies to be listed on eBay. Unauthorized copies may include things that are bootlegged, illegally duplicated, or pirated. These kinds of things may infringe on someone's copyright or trademark.
To read more please go to Link hidden: Login to view
Might be best to start researching for a better niche to consider :)