I am pretty sure any joystick out of Galaga UR cab would work.
A Galaga joystick is a 2 way stick and Mrs Pac is a 4 way. Although the Galaga control panel restricts to 2 way movement, the mounting bolts might be different.
Yes the bolts are very different I have a few spare sticks out of Pac's and a Galaga UR's but was hoping to find a good working orig or replacement to fit the holes...I'm surprised there is nothing.