who do i contact to make custom plastic cassette cases and shells?

Fuji for one.. LOL are there Copy rights? I'd doubt it..

Don't stop there. Reel to Reel to.. Pre recorded with a GREAT new medium all for a reasonable price.. You got my vote..

Regards

Unless you can find the original injection molds for those cassette cases your in for a rude awakening on having new molds built. Plastic injection mold are not cheap. The original molds were probably at least 24 cavity and designed for a fast cycle time.

I would look for an existing manufacture, probably in China and talk to them.
You would need a huge market for the finished product to even think about starting from scratch.
Where will you source the tape from? High quality recording tape isn't commonly available these days.
BillWojo

I vote thumbs down.

party pooper..