Try and find a tire size chart (I've seen folks post them here before, try a search or an online tire place). Then maybe see if there's anything remotely similar to a 16" or 15" tire. The chains don't care what size the rim is as long as the whole wheel/tire combo fits the chain. Just a suggestion...
Also, just in case you do find a set, make sure you have enough clearance between the tire and the fender...I've seen what a loose chain can do (not on my rig). OUCH!!
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Cheers!,
-John