I got Mad Stalker from Strictly Limited Games. I have a few other Genesis carts from them and they put out a quality product. Even though they're based in Europe, they cater to an American market as well. Although if you ever preorder something from them, you'll probably wait a long time, like with Limited Run. I know Strictly Limited also released a European Mega Drive version although IDK if it has any difference aside from the package design. I think Mad Stalker was first put out by Columbus Circle on MD in Japan, but I have a couple of their other games and they weren't beveled, so I'm hesitant to pick up any more CC games.
I haven't played much of the game yet, but it seems pretty cool! I like beat 'em ups and robots and it's got both those things along with some very cool music!
I think it's amazing that modern companies are licensing unreleased Genesis games to put out official releases on quality carts that can play on real hardware! It would be better if Sega would actually let them use the "Sega Genesis" trademark, but I feel like that kind of thing could be possible in the future.