The brace you get from BMW with the BMX-style foam will fit the bars, got mine from the dealers and cost about £33 inc VAT if i remember rightly. (that was just for the brace bar, not the foam cover)
Just bolts straight on, no need to remove anything, takes literally 2 mins
I bought mine a couple of months ago, I think it came in around £55 for both parts. The only thing you will have to watch is if you use a tank bag. I fitted mine then a month later went on my summer trip and was horrified when my bag wouldn't sit right.