I picked out two very important words in Tom's response: "Plumbing Supply"
My experience is that it's well worth visiting a plumbing supply store for parts like these. I've found that even though the parts look "about" the same, there can be countless possibilities--only one of which works. The "big box" home improvement stores will have a few--but probably not the one you're looking for.
Saves trips, time, and anxiety!
Have had with them.