Race/Warband Specific Items: I would argue that there is never a penalty in finding a race/warband related item, as that gives them a disadvantage. Thus, a Lustria Amazon warband in Mordheim City has no extra penalties finding their specific stuff. (Sure, it seems out of place, but you're the group that let them play in the first place!)
For the rest, I'd argue on how "specific" it is to that location. Cathayan Plate Armor would be at +2 / Impossible to find outside of Cathay, but Telescopes (from Relics) are found in every big city. If need be, go item by item and make a call.
As one of the writers of Sartosa, I'd recommend that any items introduced in Sartosa are "race specific" to any form of Pirate Warband, regardless of city. Likewise, all Sartosa items are available in any Maritime campaign setting, (Lustria, New Ind [Kurst's Lustria / Sartosa merging], Marienburg- although werekin is certainly allowed to veto that, as it's his setting!)