DVD-R question

My DVD burner can do dual-layer but I haven't seen any dual-layer DVD-Rs about. Are there any and how much do they cost?
I'm slowly getting to a point where all the files of a photoshoot (originals and edits in various versions) won't even fit on a DVD for backup purposes...

They can't beat Oxford but they can beat the world

Last weekend, the Cambridge team beat the German, the US and the British national teams at this rowing event in Germany

My hovercraft is full of eels

Complete scripts of Monty Python's Flying Circus