I replaced mine with an LG Blu-ray burner, and it's been perfect for four years now.
I also have the two original Superdrives this unit (a 2009 4,1 Mac Pro) came with when I custom ordered it from Apple, and both have barely been used, and zero use to me. They are both in perfect condition (about as close as brand new as you can get) and if you want one, I'm sure it would be easy enough to ship you one.