I use this and it's well thought out and incredibly well built.
http://www.chefknivestogo.com/ultima...knife-bag.html
I don't actually transport my knives a lot, but if I did and really, really needed the case I already used, then I'd probably end up buying one of these because they're so beautiful and I love anything hand made.
http://www.leather-worker.com/
There's a lot of good choices here. I bought a cheap $25 Messermeister roll and I hated it so much I just gave it to my dad who did give it some use.
http://www.chefknivestogo.com/kniflugandac.html