12 button controllers are how leverless controllers started—since you have four buttons for directional inputs and eight buttons for attack inputs.
The Zero Two is a modular controller that can be ordered in lever or leverless format—as well as preassembled or DIY form.
The Zero One is available in multiple layouts and colors—plus preassembled or DIY formats—and an overall modular design.
The Cross|Up allows you to simultaneously use a joystick and buttons to input directions, creating new possibilities.
The RAC-J800B, part of the J800 series, is an excellent all-button controller that is available in multiple variations.
Ultra Arcade's Standard series is a reasonable entry point into its customizable controllers, and there are Pro & Lite editions available.
The Snack Box Micro is a bestselling pioneer of mini leverless controllers. Its customizability and portability make it a grand slam offer.
If you've never seen a table-mountable fightstick, check out the unique KT511 Arcade Game Joystick.
Paradise Arcade Shop graces the fighting game community with a slim and lightweight controller that can fit into a laptop sleeve.