If Hintergnomes existed, Hinterpockets would be their specialty. Each hintergnome would, theoretically, be gifted with the creation of extradimensional spaces, which they might sow into their clothing. The creation and sale of Hinterpockets would hypothetically be regulated by some of guild, such as the Hinterguild of Pocketers and Bagmakers, which could possibly ensure a level of quality and safety.
Hinterpockets definitely exist, but where they come from is less certain. They're robust extradimensional spaces, less risky than conventional bags of holding or spacious pouches, and they never lose what's been put inside of them. Destroying a Hinterpocket just dumps everything within it harmlessly outside it. That's the kind of quality you might get with some sort of regulation, but given that the creators and their regulatory bodies are unknown or nonexistant, it's hard to say why they're so good.