TT does sell the 2 disc clear cases, for $1.75.
https://www.twilighttimemovies.com/transparent-2-disc-blu-ray-case/
No 3-disc cases though, you have to get them elsewhere:
http://www.casetopia.com/Scanavo_3_Disc_Blu_ray_Case_14mm_p/br3-onet.14mm.krt.htm