On the 4x5 camera I built, the plans called for using the spring metal off the back of the rubber on windshield wipers. I found an old set at the gas station and they were springy and easily bent into shape. However the tight tolerances seemed out of my league for the groundglass and back, so I ended up stealing the grafloc back off a press camera and away I went.

Contact me if you want more info.

Eric