video game characters usually only deal with established merchandisers (with serious sales voodoo). Also, they often enter into exclusive licenses. That means they can't grant permission to you without violating their license with someone else. It's possible that if you were offering a new product category, you might have a chance. But that's tough to pull off. (PS. Here's the lowdown on trademark licensing.)
How do other people get away with it? It's a matter of odds. The owners of valuable character properties usually put their resources into pursuing the bigger fish, and for the most part, that often bypasses individual sales at Etsy or eBay. So, unless the trademark owner is intending to make an example of a small fry infringer, a cease and desist letter may be sent, and that's sometimes the end of it.
What should you do? We wish it wasn't frustrating to get permission. Like, wouldn't it be great if you could pay "per impression" for reproductions of licensed characters. Of course, that may blow any standards of quality ... but hey, merchandise happens. Anyway, infringement is always a gamble and we'll leave the risk assessment to you.