Go under ground using your Explorer Kit
In Iron Island or underground
Iron Island.
You can find shiny stones on route 228 and Iron island
Togetic into Togekiss and Roselia into Roserade
at the end of the cave in canalave city
there are 2
Shiny Stones weren't invented then. They're Gen. 4, Gold is Gen. 2.
In the Pokemon underground. Shiny stones can be found on Route 228 or on Iron Island in Pokemon Diamond and Pearl. In Pokemon Platinum, there is also one on Route 210 that can be found with the Dowsing Machine.
the same way as platinum
To find a shiny stone in platinum you have to dig in the underground tunnel.
there is no such thing as a shiny berry.
you can get more shiny stones underground like fire, leaf, water, moon and lightning stones, but some stones need specific places underground.