Unless you get a notebook slot-loading drive and get an adapter so you can stick it in a 5.25" bay, the only one you can buy new (to my knowledge) is the Plextor PX-716AL.
I have one, and while the first one died on me, the replacement has been running with no problems since I got it.
As Crespin stated, the only modern DVD-RW drive is the Plextor 716AL - which is no longer in production unfortunately. Besides a slim notebook drive and a 5.25" adapter, there's no way to buy one new.
I had 3 of the Plextor drives and sold 2 of them on Ebay and kept 1 for my current build. You can look on Ebay to try and find one, however, they are pretty scarce these days.
Here's what the Plextor looks like (my current build)