I have had a Moen sink for over 10 years, I have literally replaced the entire faucet over the years for free through Moen because it's guaranteed for life. Tell them the problem and they will figure out what part you need and ship it to you.
Moen has a web site which gives you all kinds of choices for parts. Also there is a toll free number on there. We ordered a small part for bathroom sink and they didn't even charge us.
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