Check Dollar Tree for screen protector film. I have mine in a plastic clamshell from there, too, and a simple foam padded sleeve. I did have to prowl a couple of stores to find everything, so patience will help. But it means I have screen protector, clamshell, and sleeve for $3 plus tax. They don't look fancy, but they do work.
For the adaptor, I don't know of a good cheap option.