I bought some round magnets and used them to hold 2 Brinkmann charcoal pans together. Each magnet is 5/8" high, a nice compromise between the recommended 1/2" and 3/4" spacing. Works great...!
Good point, Rusty...! Unless I'm mistaken, most permanent magnets are made of colbat, iron and nickel. So I got their Curie temperatures in kelvins and converted to fahrenheit: