Product review (5 stars): A great and inexpensive replacement
I purchased my unit from "PartsAway" for $56.92, free shipping.  (Be careful; some vendors charge much, much more for the identical part!)  Yes, there are slight model variations and with some dishwashers (mine, for instance) there was a slightly larger gap between the unit and the front panel.  Not to worry; it won't leak if you are careful to have the gasket properly smoothed down on the dispenser assembly and to tighten the screws GRADUALLY and EVENLY and torqued the same!  There is an on-line video showing how to install this unit.  Do a web search for "video whirlpool dishwasher rinse aid dispenser" (without quotes) to find it.  Replacing this unit totally solved our leaking rinse aid problem.  I took apart the old unit and saw that it was leaking at the valve assembly; not easy to fix.  I think that allowing the dispenser to "run dry" of rinse aid might have contributed to the problem.  Good Luck!