Call a wrecking yard; tow eyes are the kind of things people leave in cars and i bet they'd only charge a minimal amount. FWIW, I'm pretty sure the tow eye for my Mercedes was the same size as the one for my BMW. Makes me wonder if they're all a standard size. Does your wife's Cobalt have a tow eye, and if so, have you tried it? Regardless, pick one up when you get the chance.
Taking the wheel off is prolly your cheapest option, though. Hope you didn't damage the wheel...