I've never seen or heard of a purpose made case for such things. A suitably sized padded case designed for something else could certainly be used, though.
There are no particular techniques, just general caution. Don't drop them, don't squeeze them(many are quite delicate with respect to pressure), don't let them get dusty. That said, I've seen a fair few users who just shove their modules(the old curved Dell ones, floppy and CD drives) into extra pockets on the laptop bag, and they survived a fair while.