If you can get by with just a joystick, then wiring a joystick up to Marlin is the way to go. You did not say what control board you use, but I believe I’ve seen topics on the forum where a joystick has been added to the Rambo board, SKR Pro board, and Ramps board. If you use one of these three boards, these topics will help you identify the correct pins. I do recommend purchasing a decent joystick. I’ve seen a post or two where the OP attempted to use a cheap joystick like this, and they were not happy with the result.
If you search Thingiverse for"MPCNC Pendant," you will find several projects. I created my own pendant and used this Thingiverse project as my reference. An external pendant requires access to a serial connection on the control board. Not all boards have an available serial connection.
Recently Steve Potter opened a forum topic about his wireless pendant.