If you have been a pad player for a long time, the easiest transition for you may be a controller with a D-pad on the left and arcade buttons on the right.
Available in preassembled & DIY formats, the PadBox is a plastic D-pad controller with Sanwa buttons, Omron switches, and custom LED.
Cubs made a hybrid, the Cubstraption, that has a GameCube controller on the left and half of a box controller on the right.
This slim mini controller combines a D-pad with arcade buttons in the Noir layout and has a grip on the left side.
The VANG propad is a leverless controller that is a solution for pad players who would like arcade buttons without sacrificing the D-pad.