I currently use a 110qt Sterilite for my 5 foot female. Dimensions are 35 x 19 x 13.
I should probably get some of those clips. She's never even tried to escape from this tub that I know of, though, so I think I'm in good shape at least for the time being.
http://i1142.photobucket.com/albums/...ottark/tub.jpg
http://i1142.photobucket.com/albums/...ttark/tub3.jpg
http://i1142.photobucket.com/albums/...ttark/tub2.jpg