If by Fusion you mean Kega Fusion (I doubt this a lot) the Joystick handler supports both keyboard keys and joypad buttons at the same time.
Personally I suggest a Sidewinder, because I have used about 3 and they've never failed me. Unfortunately I have a feeling most are game port based.
This is a problem for me too, as I no longer have a game port and instead have to use USB. I only have one USB pad but plan to buy more for 4-player Micro Machines 96 gameplay
or V3, whatever floats the boat. My keyboard only supports a measly 2 players simultaneously, at best (my laptop supports 4, which is ridiculous)
To put a spin on this: cheap online USB joypad stockists?