A cheaper alternative is to forgo the clamps and just anchor the shade cloth with rocks or sand bags on either side and at the ends. I am a big fan of the wire-loc system but for you to invest in that for PVC pipe would be like installing wood flooring in a tent.

I think you could make your own clamps by cutting pieces of pipe long-ways and screwing them down.

do you have to use 1/2" pvc? this isn't shade cloth just netting. the edges are held down with sod staples here and there.

I like the clamps because then 6' wide shade cloth can be used, only really need to shade mid day full sun. We don't have much wind in the summer/late summer, fall?winter is another thing!

Cheaper is to run heavy twine down the hoops and tie it off every few hoops then use regular clothes pins....good if not too windy.

For plastic, the dirt or milk jugs with water or rocks work. I put one side of the low tunnel down for the duration of the crop with dirt and weight the other with one of the things suggests the other side at every or every other hoop.