I adore Itoya portfolios and the company also recently came out with new sizes. (I have wanted a 16x20 size for SO SO SO long it's not funny. Now they have one! ^_^) I'm lucky that I have an art store near me which orders in whichever sizes I want. You can see what exists here:
http://www.itoya.com/ and you can usually find them for sale on Amazon and such places. I prefer the "Art Portfolio Presentation Album" style myself, but they have lots of options. I can say that the 11x14 size Presentation Album will fit over a standard (by US sizes, at least) hanger and I do hang some of my books in my closet.
Note about hanging them: Remember when you hang books in your closet to REALLY check your closet bar. Filled cel books are heavy! When I used to hang all of mine, I wound up collapsing the bar in my closet twice -- the second time was even after my husband had reinforced the bar with lead piping and sank it into the walls by several inches.

Since my husband was tired of my fretting about the strength of the closet bar, he made me a set of shelves specifically sized for my 11x14 Itoyas. That is what I use to store most of them now, on their long side, standing up like books, and never packed too tightly. (Always make sure you can fairly easily slide your fingers between any two books.)
For bags, I really like Heiko. They're not the only bag out there, but they come in an amazing number of sizes and I really love how easy they are to get. You can order them right here:
http://www.heikoinc.com/ I like their "Clear Poly Bags Sleeve", for which they also have a self-seal variety. (But I found more often than not, I didn't want to seal them with the seal strip, so I stopped getting the self-seal ones.)
Random side note: I never frame cels because the few I've briefly had framed were all damaged by light. (Even when displayed away from direct light and behind UV protective glass.) All that I had in frames, I took back out of the frames. Be very careful if you frame!
Good luck!!
