The big factor here is going to be the bolt pattern.
I think the original sticks in those were Wico sticks.
If so, the Seimitsu, Sanwa and J-sticks won't fit without redrilling.
Most of the Happ sticks, and I think all of the Wico sticks, will match the bolt pattern.
You can get replacement balltops from Groovy Game Gear for both the Happ and Wico sticks.
There are even some NOS Wico replacement balltops available out there.
Buttons aren't as critical.
You may have to do a bit of grinding on the buttons or holes, depending on the exact fit.
Leafswitch buttons will likely need the tabs ground off to fit through the holes.
My personal favorite buttons are the flat-top Seimitsu buttons.
They are a mini-leafswitch inside, rather than the flip-flop microswitch of the Cherry switches Happ uses.
This makes them feel a little more responsive to me.