The individual L E D's are not replaceable. I bought the whole light bar on ebay for about $150. I was able to replace it myself with a minimum of work in half an hour with a couple of simple tools. Need to carefully access the rear from inside the trunk by carefully lifting the inner lining. Do not over-tighten the bolts. I have been careful when closing the trunk. I'm convinced that slamming the trunk lid is what does them in.
When I replaced mine I tightened them down a bit to snug and sure enough some of plastic that holds the screw lugs cracked from the housing. Also make sure the gasket material seals up against the trunklid or you could get leaks