A 12" acrylic riser might work as an iPad scanning stand or document camera stand, and it would not block light from the document. You could even turn it on its side in a "C" orientation to slide books underneath the iPad for scanning. One drawback is that it can't be folded flat and slipped into a backpack or briefcase, like some of the other products shown.
PVC pipe iPad document camera / scanning stand - One of the best and most inexpensive DIY designs I've seen. This YouTube video is a slide deck with detailed instructions. It goes by fast, so hit "Pause" on each slide to read the text.