12 button controllers are how leverless controllers started—since you have four buttons for directional inputs and eight buttons for attack inputs.
The Snack Box Micro Lite brings you a lot of the original Snack Box Micro's awesome features, but this time, it's nearly twice as light.
The HING3DBOX is a 3D printed leverless controller that you can fold in half for easy carriage and storage.
The KeebBrawler-01 is a mini stickless controller that most notably has a wide jump button and unique attack button layout.
Certain Deth is a Detroit-based outfit that provides custom enclosures and builds with key, button, or joystick directional inputs.
The Neobox is an enlargement of the open source Flatbox. It also spares you from building a Flatbox yourself.
The Slab Mini All Button Controller is a sandwich acrylic case controller with hot swappable sockets and LED.
Arborcade makes classy wooden controllers without sacrificing performance, such as a walnut or mahogany controller with Sanwa buttons.
The Stress Pocket Arcade Fight Pad is a mini WASD controller with unusual angles that may appeal to you more than the usual layout.