http://www.ohare.com/PDF/PassengerIn...1terminal5.pdf
That shows lounges for SAS, British Airways, Alitalia, Aer Lingus, JAL, Air France, Korean Air, Swiss and something called the "worldwide VIP lounge".
Please have a look at their websites and let us know who offers the cheapest one day pass for their lounge.
Another thing to consider is that with a 5hr layover, that's plenty of time to head to another terminal (where you'll find lounges from domestic airlines).