There's two major caddy styled back then that were commonly used. One that was like a CED cartridge and the cartridge itself had a spine that held the disc, and then there's the CD-CADDY which looks like a modified Magneto Optical disk (note how it still has write protect tabs). Aside from a few oddball vendors that used the former, everyone used CD-CADDY and they're cheap to get.

Here's one for $3.