Rust-Oleum® Automotive High Heat Spray. This flat, protective enamel bonds to bare metal and withstands intermittent temperatures of up to 2000°F (1093°C).
Auto Specialty Paints High Heat Product Page
Some have had luck with barbecue / grill paint. Rust-Oleum® Specialty High Heat Spray retains color and finish up to 1200º F. Apply to grills, wood-burning stoves, radiators, engines or other metal items. Provides rust protection.