I've never used box blinds before but I bought a couple and had them put in this week. I still favor sitting in the open either in a ladder stand or on the ground but these will sure be nice when it's raining, sleeting and cold.
I bought those from Jim Sobolik, Trophy Buck Food Plots, from Deer River, MN. He has a MN guy who makes them and Jim put them in place for me. Well made. 4x4 base, box framed with 2x4's, heavy rubber roof. All treated wood. They should work well.
Those are 4x5. I'm pretty sure he orders whatever his customers want for the year and picks them all up at once. I don't know that he stocks them up. Check out his web site. He has a gallery of pictures of different stands and give him a call.