There is one in route 34.
Ercuteak city need to use dowsing machine
Olivine city need to use dowsing machine
Radio tower earn 25 points at Buena's password
Mt.Mortar, Tin Tower, whirl island,Mt. Silver and the shinning light house you will need to use the dowsing machine.
Route 27, 28, Cinnibar Island, Indigo plateau, Cerulean cave and Victory Road you will need the dowsing machine.
Vermilion city fan club president.
Johto battle frontier shop, Pokeathlon Dome.
Shinnoh field 5000+, Sightseeing 5000+
Hope this helps