I found a nice travel case for my Eton E5, and I didn't have to spend any money because I already owned it:
There's about a 3/4" gap along the top, and a 1 1/3" gap along the side. It's a snug fit top-to-bottom.
I checked Amazon, but didn't see these for sale there. I bought it a few years ago. It was made by A.L.S. Industries Inc. from Torrance, California.