I make my own out of 2X4's. Very solid, easily repairable, can set up in all kinds of weather, and are modular. These are pic's of the first ones I made. I now drill the hole for the bolt at an angle so the plate is angled downward. I also don't tighten the plates tight to the bolt, so it sways backward a little when hit.
I am not 100% sure, but those stands you mentioned are for 1X2 furring strips. Great for paper, but a good steel plate will break them pretty fast. Oopps my bad, I see they offer them in a 2x4 model for $80. If you go that route, get the 2X4 model.
Two 27" side -Two 15" middle and Two 5"- plus 48" standup with bolt angled 15 degrees down.
Steel stand - two 2x4's @ 2.56 per stand
Steel stand -One bolt 1/2" x 4 1/2 $1.08, three nuts .60, four washers .80, six 3" decking screws
Notes: For the 48" standup post, I took a palm sander and kind of sanded it down so it goes into the middle hole section easier and removal is easier also. I also carry with me two 3/4" wrenches (one open end), plus a small scrap 2X4 piece and a rubber mallet in case I have to push out the upright part from the bottom. Sometimes on a cold snowy day, it just helps.
Jay