Try the vendors that sell brake upgrades. I've seen boxes of refurbished calipers- even the mostly-useless rears- at PPC-Carson City and I have no doubt there are others. Note there is one (1.0) square o-ring seal on each piston. If you replace them and still have a leak, its likely because the mild steel piston has a corrosion nick in the plating. Such calipers need new or at least un-marred pistons, plus the seal kit, to work leak-free.
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