I'm thinking your best bet is the Smart Center. If you're in Illinois, Smart Center Lake Bluff should be very close by. If they don't have it or can't get it in 24 hours, they might be able to tell you if it's a generic size.
Do you have a Autozone close by? When I needed a new plug for another car the guy pulled out a drawer and he had a huge selection of generic plugs and found one that matched. You might want to give them a quick call and ask.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.