Bart,
Why the fudge do you need to buy the entire assembly? Does Merlin not have just the plastic piece that you need? I think that I've borken the same part that you are talking about and it was like $1.50 from Merlin.
Are parts getting that scarce?
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless