I replaced mine with a rackzilla. couldnt be happier, call Matt at atvoutfitters for the best price. The stock unit might be rebuildable but there is no kit available so you would have to find the parts yourself and polaris only sells the whole rack.
Look at the GearOne rack for the RZR. I have it on mine and it's top notch. It's all billet construction & is rebuildable. It's a bit more than the Rackzilla but if you look at the two side by side, IMHO there is no comparision.