The nice local black market of Myosotis. It specializes in selling morally dubious goods, not services. If you want services like hitmen, you'll have to go somewhere else, sorry!
The Bazaar does have you covered if you need to buy some sort of drug, meat from exotic creatures (long pig...), a fun new homunculus friend, illegal weaponry, or whatever other goods you can't get anywhere else!
The Midnight Bazaar is not exactly a location, it's more of a network of people selling things. Theres a few websites in the deep parts of Hereafter's internet that serve as storefronts for the Bazaar that make purchasing things easier. Think of those weird dark web websites that sell drugs.
The whole network is led by 7 anonymous individuals, each specializing in a different service. Their identities aren't too well known outside of the most powerful people involved, though memes and conspiracy theories about popular beings in Myosotis being a Midnight Bazaar leader are quite popular.