I really wanted a ball-top joystick like the original Pac-Man and Ms. Pac-man games, but decided finally on an E-stick from
www.ultimarc.com . Authentic Pac-Man and Ms. Pac-man 4-way sticks can be had from Happ Controls and Ultimarc also has the J-stick which is pretty much the same thing, but the E-stick is the only one that can be rotated 45 degrees so it remains a 4-way stick but hits only the diagonals for games like Q-bert and Congo Bongo. If you don't care too much about diagonal-only games I'd go with a 4-way only stick like the Pac-man sticks from Happ.
You also have the option of Oscar restrictor plates that will turn an 8-way stick into a 4-way, but if you've got the space on your panel for a 4-way I'd just get a true 4-way. E-stick gets my vote for the diagonal option, but it's not nearly as cool-looking as a true Pac-man stick with the ball on the top instead of the long tear-drop shape handle.