Where to Find and Catch Mime Jr.
From Pokemon Go Wiki
Mime_Jr. are found and captured in Nest and Habitat locations.
Nests
Mime_Jr. Nests are locations that consistently spawn Mime_Jr..
Habitats
Mime_Jr. Habitats are spawn locations where Mime_Jr. is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: