said by pende_tim:
Could you try taking it apart, noting the sequence, and soaking it in vinegar? That will clean most of the lime and crud out. I may work after this treatment.
Is there a real plumbing wholesale distributor in the area? Like one where you see "Joe's Plumbing" tuck parked getting supplies? They may have parts or can put you on to where to get them.
The problem is the plastic itself has degraded to a point where it no longer stays inside the metal housing, so we'd need a complete replacement (even if it was just something we could put inside the housing). I was planning on heading down to my local plumbing supply place tomorrow, but figured I'd hedge my bets by posting this thread ahead of time. Thanks for the suggestions!