tirerack.com is much better than most everything you find on eBay.
If you are willing to buy new tires, then I would look for bigger wheels, maybe 17"s. I feel like that would make the expense worth it. However, since you only have the bottlecaps, and you already have the rubber (which I guess your tire guy would mount and balance on your new 15"s), this may work out.
Also, those places usually relist their postings, since they have more than one set available for sale.
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