I never have a problem getting jars at the local thrift store.
You’re lucky. The last 2-3 years, I haven’t found any good prepping things at the big community sale so it may be people are waking up and keeping it for themselves. No camping or outdoor stuff, very few gardening or food storage books and no generators or food dehydrators or hand crank kitchen items though lots of Christmas decorations, older worn clothes and fiction books. A couple years ago, I noticed a big change in items but last year it slapped me hard. Times are changing.