Dean Collins marketed these as Lightform Panels and they were sold by Bogen, until recently. You can occasionally find the Lightform Double Clips on eBay. Calumet still sells their light panels and sells the Panel Joiner Clips for 11.99 per pack of 6. I have a bunch of these that I have picked up over the years, mostly on eBay. The photoflex panels are similar, but I don't know whether they will work with Lightform or Calumet panels. Both Lightform and Calumet panels use 3/4" plastic pipe frames, but they appear to be ABS instead of PVC. PVC seems to be a little less rigid. I have used 3/4" aluminum electrical conduit in place of PVC pipe and it is quite a bit more rigid, but it is hard to find and expensive. I have made a couple of 78" square panels this way and adapted one to hold an 8' X 10' mesh tarp. When they get this big, they get really floppy and need quite a bit of support.