Replace nav DVD laser?

[asma123]

Alright guys I got a 2007 e70 x5 4.8.
Since I've gotten the car I've always had an intermittent issue with the dvd not reading and sometimes long boot up times. Mostly I get the DVD error or the insert dvd message.
Now, my dvd is a burnt copy. When I first burnt it the drive read it fine no problems and it updated as well. Just lately I've been having issues with it almost not reading all the time.
many people experiencing the same issue suggested replacing the drive or the laser. I'm looking for the best cost efficient way.
I took the dvd drive out today completely and I cleaned the lens. It did help but still needs to be replaced. Any ideas where I can get either the lens or the dvd drive?