You can order the struts as a kit, or make your own out of thin steel rod. I stole this hardware off of a set of fenders from the 70's that I had laying around. I wish the struts were a little bit longer. I made a set for my old Trek FX a few years ago, but they weren't nearly as nice as these.
That's exactly why these are not going stomping. Strictly for when I'm commuting around town.