Take a heat gun and slowly warm the glass up until you can pry the edge with a thin item like a metal pick. Once it's up scrape the old glue out. You can order a piece of 3.5 inch glass from any call maker supply place (I'm assuming it's 3.5 inch but make sure you know before you order). I generally use Brookside. Understand this time of year suppliers take longer to ship. Once you have the glass run a bead of plumber goop around the lip then clamp it down for at least 24hrs. You can also use a chunky soup can and set it on top. Then you should be set. If you don't feel confident doing this I'm sure many of use that make calls would be glad to help. It's a pretty easy fix. Also an fyi be careful not to over heat the pot as it can damage the finish. Let me know if you need any other help.
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