Swampert_dude

Best answer as chosen by Asker / Ratings
Here is where you can obtain the items you need:

Blazing Gem: Agrabah - Kill the Fat Bandits.
Frost Gem: Agrabah - The Icecube Heartless drop them, you can find them in front of the enterance of the Chasm of Challenges.
Dense Stone: Sniper Nobodies - Found in The World That Never Was, in the Hall of Empty Melodies (Where you fought Xigbar)
Dense Stone: Samurai Nobodies - Found in The World That Never Was, Naught's Approach.
Dense Crystal: Beserker Nobodies - found in The World That Never Was, Addled Impasse (Where you fought Siax).
Twilight Stone: Dancer Nobodies - Found in The World That Never Was, Naught's Approach, or Twilight Town Mansion, in the Basement Corridor.
Twilight Gem: Assassin Nobodies - Found in The World That Never Was, Hall of Empty Melodies, not where you fought Xigbar, but the other part where you reunite with Kairi and Riku.
Twilight Crystal: Sorceror Nobodies - Found in The World That Never Was, Nothing's Call or Ruin and Creation's passage.
Energy Gem: Emerald Blue nobodies (The ones that create tornados) - Found in Agrabah Bazaar or the Fortune Teller Nobodies, found in Agrabah, Cave of Wonders.
Serenity Crystal: Assassin Nobodies - Found in The World That Never Was, Hall of Empty Melodies, the second part OR Samurais Nobodies in The World That Never Was, Naught's Approach.

Phew..Hope I helped! :D