Where can I get a **CHEAP** replacement donut spare for a 2008 Scion XB (5-bolt)?

The moron who had the car before me drove the old one down to the cords. The dealer is SUPER expensive, I've been trying EBay and Craigslist and I've inquired at EVERY junkyard within 100 miles of me. This is frustrating. Are there any decent cross-referenced ones?