Everywhere! I mean, not literally, but you can find them in lots of places.
-There may be a local zine fair where you live
-Ask your library if they have zines!
-Your friend could be a secret zine maker! Ask them! Do a zine swap!
-People sell them on Etsy
-People sell/share them on Gumroad! (Some are pay-what-you-want or free)
-People sell/share them on itch! You can even read some zines directly in your browser!
-Right here on neocities! For example at: https://quarantinezineclub.neocities.org/ or by browsing the zine/zines tags
And if you think a zine for something should exist, but it doesn't, you can make your own!
Know any other good locations I've missed? Drop me a message on my neocities profile and let me know!