I bought some on eBay a couple weeks ago; a three-pack from China for about $9, to test with my new color laser printer. They have smooth plastic sleeves, not the textured plastic of the originals, but they lock closed properly, and look alright, so they work. They even have the rack-tags on them. So, while they're not perfect, they're still pretty good, and not horribly costly. Too bad you can't easily get replacement Saturn/Sega CD cases, but those were a design nightmare anyway.
Found the item on eBay:
http://www.ebay.com/itm/221979982411