Folks might be interested in a small game controller, the 8Bitdo Lite Bluetooth Gamepad.
I’ve been using it with a drawing program, but I think it would work well with Renoise.
It fits in my hand easily (I actually hold it sideways) so I can draw with my right hand and manage brushes, undo, saving, with my left.
I use it with a small program called JoyToKey: