the shiny stone can be obtained in four ways in this game and it's counter part: Heart Gold.
1- It can be bought as a prize from the pokeathalon dome on the following days:
Sunday
Monday
Wednesday
Thursday
Saturday
2- it is a 1st place prize in the bug catching contest
3- a trainer called Bird Keeper Josh can give it to you
4- probably the easiest way, there is one sitting around in the National park. it requires rock climb to get to though, so you need Blue's gym badge.
I do hope this answer was useful to you.
To find a shiny stone you can trade a pokemon thats holding the shiny stone or maybe someone in your pokemon game will give you one. If you use a Shiny Stone on Minnico it will evolve into Cinnico
You can find a Shiny Stone at Route 228 and also at Iron Island
you can get a shiny stone in iron island when your exiting iron island go to you right
End of Iron Island
End of iron island
you find the sihny ston in mewtoo's cave
You can find a Shiny Stone in Route 228 in Pokemon Diamond and Pearl. In Pokemon Platinum, you can also find a Shiny Stone on Iron Island.
You can find a Shiny Stone in route 6.
To find a shiny stone you can trade a pokemon thats holding the shiny stone or maybe someone in your pokemon game will give you one. If you use a Shiny Stone on Minnico it will evolve into Cinnico
if you dig underground you'll eventually find thunder stone then after a while you'll find shiny stone ;^)
You can find a Shiny Stone at Route 228 and also at Iron Island
In the underground.
in iron island
You find it in the chargestone cave
Iron Island.
route 1
by the Pokemon center.