eBay is probably the only choice to find used ones. I've bought a few used 350s and mostly have been very happy with them, although one blue one had a really badly damaged screen, even had 2 gouges in it (have no idea how they managed to do it). But since I was dying for a blue one, I swapped out the screen. A few of them were in pristine condition and came with the cover.
Just email the seller with any questions, specifically asking about any scratches or anything visible on the screen. Ask about the stylus also if that's important to you. The damaged blue one also had no stylus, I'm sure they broke it. I'm not sure if the replacement stylus that chris77586 set up for us Sony users will also fit the 950.
Edit: You might also check the
Flea Market section here towards the bottom of the forum and check if anyone is selling one, or make a post inquiring about buying one.
In fact, one recently was posted here for sale with a very nice cover:
https://www.mobileread.com/forums/sho...d.php?t=224151