I have finished my upgraded “Pro” version Vectrex controller. I managed to find a nice feeling large analog joystick, one that I could just barely squeeze in the form factor. It was designed for drone control, so it is very sensitive as well. Unfortunately it is so tall it does not quite fit in the front of the vectrex anymore, but if you really wanted to you could shorten it. Also being black rubber around the stick, I can’t make it light up. (BUT I can use glow in the dark filament now for the rest of the controller if you want!) The part is $15-$20 more then my current joystick choice, so if you want one, they are $115.
If you would like one, you can fill out this order form.