Where to Find and Catch Seismitoad
From Pokemon Go Wiki
Seismitoad are found and captured in Nest and Habitat locations.
Nests
Seismitoad Nests are locations that consistently spawn Seismitoad.
Habitats
Seismitoad Habitats are spawn locations where Seismitoad 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: