Found mine on kijiji (more popular than Craigslist here in Canada). One was from a guy who didn't have room in his man cave and the other 2 cases were from a guy who used to own a snowboard/bicycle store. Keep looking often and you'll find something.
I've scored 6 cases in a little more than a month. Look EVERY day. Pay a visit to opticians as mentioned above. The one I found this weekend was sitting in the back office with some junk. The owner just wanted to get rid of it. eBay is ok but remember these are large and shipping will crush you. Be willing to drive. Talk to as many people as you can. It's amazing how one lead turns into another. Condition is a big factor. Don't overspend. I've seen lots of cases priced at $1000 and slowly the price starts coming down because no one will touch it. Bike shops, ski shops, outdoor and fitness retailers. Oh and one last piece of advice. Stay away from my territory. I'm getting all of them before you do. Ha!
I'm not trying to be a ****.....but if you can't find this link that was so easily accessible by a few clicks in the display case discussion.....how are you hoping to get the actual legwork done to find a case?