You can get it in Johto by coming 1st in the National Park's Bug catching competition,
You can also get it by winning events in the Pokeathlon Dome
In Kanto, one way to get it is to show Bill a Marril In Heart Gold, or show him a Staryu in Soul Silver
Or you could just wait for the Girl on Route 42 to ring you (if you have her number) she gives you items, mainly evolution stones.
Chat with our AI personalities
Yes, use a water stone.
In order of how he wants to see them (based on Heart Gold and Soul Silver): Gold/Heart Gold: Oddish - Leaf Stone Growlithe - Fire Stone Pichu - Thunderstone Jigglypuff - Everstone Marill - Water Stone Silver/Soul Silver: Lickitung - Everstone Oddish - Leaf Stone Staryu - Water Stone Vulpix - Fire Stone Pichu - Thunderstone
use a water stone o evole it
You need to get to Bills Grandpa in Cerulean (Kanto), he will ask for a pokemon. The first is Lickitung, the second is Oddish and the last is staryue, i think that you then get the water stone from him. I hope this help :)
you can use a water stone on lombre