First I will tell you where to get the normal Orichalcum. You get it from a rare hartless called the  "Bulky Vendor". All you have to do is use the reaction commands.

 

The seven orichalcum+'s are written where to find them below.

 

The location for this Orichalcum+ is in Atlantica, just progress thro-

ugh the chapters in that world, you get it after chapter five.

 

This Orichalcum+ is located in the world space paranoids, just get to the MCP area and it's in a small chest near the computer. 

 

Orichalcum+ # 3 is located in Olympus Coliseum, you have to win the fourth trophy, "The Godess of Fate". You will also get a keyblade.

 

You will get this Orichalcum+ when you fully complete pooh's storybook, chapter five.

 

This Orichalcum+ is found in a small chest in the "Sunset Terrace" in Twilight Town. The chest is on a ledge so you will need to use the train to hop on to it.

 

The location is at "The Brink of Despair" in "The World that Never was". It is in a small chest. The chest is on a little cliff, to get there face the nobody castle entrance and turn left, there should be a building,then a little cliff, look closely and you will find it.

 

This is the hardest Orichalcum+ to get. First you will need EVERY moogle synthesis material. The kinds are:  Blazing, Lightning, Frost, Dark, Dense, Twilight, Lucid, Power, Mythril, Bright, Energy, Serenity, and the normal Orichalcum.

You will need all of the Shards, Stones, Gems, and Crystals of the materials listed above(exept the Orichalcum). After you need to cash them in to any moogle synthesis store and the moogle will give you one Orichalcum+ in return.