Fiber Powder for DIY Quest Bars?

I've been making this recipie ( http://www.sweetcheetah.com/2013/07/diy-quest-bars.html ) for Do-It-Yourself Quest Bars and have had a lot of success as they have turned out really good. I've been using protein powder from Sprouts (their Whey Isolate from the bin) and Oat Flour. I want to try to up the fiber in these bars but don't have any experience with fiber powders. Anyone have any recommendations? Kirkland brand? Psyllium? Hemp?