Some distributors sell a short 4-bolt chain tensioner which some say help it from getting dragged into your spokes at high speed by the chain. Maybe one of those and an upgraded bearing type idler wheel or skateboard wheel or one of the many DIY solutions. I also hear if you replace the rag joint with a floating hub adapter from manic mechanic, piratecycles, king's top hat adapter, or screwing sprocket into disc hub and quality sprocket you can eliminate the need for an idler completely.