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