I built my own
dodger out of 1/4" okume
plywood and glass. It's roughly 5x7, and because it was larger than a
single sheet of ply I had to buy two
sheets and assemble them together with a puzzle joint. It has softsides that can be rolled up. The picture you showed could very well be
plywood as well, just judging from the straight lines.
Mine was about $800 in materials and took probably 30 hours to build - 2 layers of glass on each side, fairing and painting. It is heavy though, probably 70-80 lbs. If I were do to it again I'd go with a foam
core.