So I just saw this thread, and I may be a little bit late, but I've been working on comparing different jewel cases you can buy and writing down what replacements match up closer to the original cases. This doc is WIP, and I found a lot of useful information in this thread/that reddit thread I'd like to include.
One thing I did find that's of note is an almost exact replacement for the Japanese Dreamcast thick cases, though you have to have the original tray.
https://docs.google.com/document/d/1gQYF24_Uf6RVPvJ_9WFphHlKUkv4poEww0VUI3DgxfE/edit?usp=sharing