I'm gonna guess you're going to need someone who can read Japanese websites to get the best prices. There are 250 Bandits in UK and Australia, but they are gray market bikes there and don't always get direct support from their Suzuki importers, so the gray market importers usually deal in their parts, too - and all these gray market bikes come used from Japan.
Indonesia got Bandit 250's direct from Suzuki importers and possibly other SE Asian nations, but if the prices these bikes sold for new are any indication of how much parts will cost, Japan is still going to be your best bet.