How can I find replacement dishwasher parts?
I agree with @BrownRedHawk: find the manual online and then look for the exploded parts view.  You'll find a part number and use that to search.  I actually find most common parts like wheels and stuff on Amazon but for this part you're looking for you may have to look harder.  I have had a lot of success with http://www.searspartsdirect.com/