Yes, these are different in every city. You can purchase conquest items from other nations if your country is ahead of that nation in conquest rank (either go to the guard in that nation's consulate, or that nation's city: T.K.,I.M. or W.W.)
Depending on what rank the country is, only certain items are available. These are three good lists for each nation's conquest items, unfortunately it does not list what rank the nation has to be for the item to be available.
http://www.koolaid-ffxi.org/linkshell/space/CP+Equipment+for+the+Kingdom+of+San+d'Oria
http://www.koolaid-ffxi.org/linkshell/space/CP+Equipment+for+the+Federation+of+Windurst
http://www.koolaid-ffxi.org/linkshell/space/CP+Equipment+for+the+Republic+of+Bastok
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Samus taught us that a girl doesn't need brains to be successful. Brains are giant, evil and vulnerable to missiles.