These are the best thick CD sleeves that I know of on the market:
https://www.uline.com/Product/Detail...Q&gclsrc=aw.ds
Downside is you can only buy them in bulk (500 minimum) & they aren't cheap.
Upside is they are almost identical to the size/weight of the "original" HouseMouseGames sleeves from way back in the day (if you ever had any of those).