there are only a few ways. get a banette with the ability Frisk,that tells you if the Pokemon you are batlin(wild or not)has a held item,at route 226 and go to mt coronet from the route 207 or 208 and go to the place where you'd use rock climb. try to find a clefairy during the morning or night because they don't show up during the day.morning or night,there is only a 10% chance there will be a wild clefairy,and on top of that,only a 5% chance there will be a moon stone attached.you'll most likely find a leppa berry.the other way is to find it underground.the only other way is to have banette with the frisk ability and go to the Pokemon mansion, talk to mr.backlot(save before you talk to him).answer yes to both of his questions andhe will say that there is a rare Pokemon,and you want it to be clefairy or cleffa.they are rare there as well.if you get lucky like me, you will get a moon stone.
Wild Chanseys or Happinys or the lost tower
happini can evolve with a oval stone
Chansey evolves from an Oval Stone.
the oval stone can be found in the second level of lost tower it is also possible to find them underground once the explorer kit is found. When found the oval stone can be used to evolve Happiny by having it hold the stone and leveling it up.
you give the oval stone to happiny and makeit have high friendship at day
End of Iron Island
happini can evolve with a oval stone
The Pokemon that can use oval stone in Pokemon platinum is Happiny. It is the pre evolve form of chansey. Mostly every chansy you catch have a oval stone.
Its not actually an egg stone its a oval stone which looks like an egg. We can find it at the lost tower on route 209.
Happiny evolves into Chansey with an Oval Stone.
galactic headquarters
Happiny during the daytime
In Pokémon Diamond, Pearl, and Platinum, a Happiny evolves into a Chansey when it is given the hold item 'Oval Stone' andlevels up. It will not evolve just by holding an oval stone.
give it the oval stone when it has high friendship
Underground
You can find the Oval Stone in the Lost Tower in Pokémon Diamond, Pearl and Platinum. Additionally Pokémon with the Pickup ability have a chance of picking it up if the Pokémon is Level 51 or higher.
To find a shiny stone in platinum you have to dig in the underground tunnel.
You give it to a Happiny and level it up during the day to evolve it into Chansey.