Looks like NAPA has remanufactured calipers for around $75 (plus core, which shouldn't be an issue). They don't show as in stock at any stores around Duluth, but they do show as being in stock at their warehouse. Might be worth giving them a call.
It might be worth checking with other stores like Advance, O'Reiley, Autozone...just see if someone can get a remanufactured caliper in today. You might get lucky. At lot of those places you can check their website to see if they show any in stock at the stores nearby your location. They're bound to be much cheaper than $300.