Amazon.com : Understanding the Nikon Speedlight: SB-900, SB-800, SB-600 : Digital Camera Accessory Kits : Electronics
Amazon.com : The Flash X-Tender (Better Beamer) FX-4 Flash Output Booster for the Nikon SB-600 and SB-800 Flashes with Lenses 300mm : Camera Flashes : Electronics