Inside an Induction Cooktop
Those coils are almost certainly custom made for the device.  It's probably made out of Litz wire as well for efficiency.  

I'm not sure if anybody sells just the coil.  However, it's just a flat wound air core coil, so it would be very easy to wind yourself if you can get your hands on some rather hefty litz wire.  Of course you don't have to use litz wire, all that does is decrease the skin effect at high frequencies so the coil is less lossy.