The 1st place I would look is EBay. I damaged mine on my RM and called my dealership who was way out of line. I than went to a few of the magazines and called places listed in the classifieds. They where at least $100 less than my dealership. I wound up getting mine repaired luckly and saved $300.
How bad is it damaged? I've had some pretty badly damaged radiators before, one even leaking at the corner seams, but I had it repaired. Many places can fix radiators for about $45, and after being mig-welded they are stronger than they were before. This is why I stress the importance of radiator braces, whether you ride MX or off-road, it's a cheap investment that will save you from a DNF or a hassel of repairing/replacing.