The one you saw with the 4 extra fins was the first Power-Fin design, my 906 has this. You don't need to find that exact one, in fact, the filter will work a little better with a little bit later style with a more open barrel - just above the skirt. The more open design lets more water flow through for better filtering... well, as good as it gets...
Does the agitator you have on the machine now have set screw? The set-screw came around much later in the Maytag family, I think in the '08 or '10 series. If you don't have one, look for a replacement that doesn't have the screw.