I am not normally one to advocate any particular product? Unless It works?
Here is one: http://www.fiberone.com/Product/cereals.aspx It's the 'original one;? Look like rabbit pellets at first? But they can and do work! Start out at 1/4 cup? w/milk to soften and then work your way to 1/2 cup... I don't suggest more at any one time? as your plumbing might just be affected! Too much too soon? I have found it to be a lo-sugar, hi fiber and almost tasty food product. Just don't start out w/ too much too soon?
Besides, it's not cardboard! Almost tastes good too. But best of all? IT WORKS! This has, does and IS working in my household. No more should be said after almost a year, should it?