I went here awhile back called SteelShell Slipcovers. They are not cheap as others, but they do protect very well.
http://www.blu-steels.com. They have ones for Jumbo steels as well. I have over 200 steels, so this is worth it and it also keeps the spine exposed only, but they slide right out. It doesn't fit the Disney Steels with their slipcovers on, but ones with the J-cards only, work very well.