Have you got a toolbox that goes across the bed of your pickup?
I've often just backed my pickup into a likely spot, and just sat on the toolbox, facing rearward (to the front of the truck).
Cheap (FREE!) and portable, so to speak. It won't get as high as some of the pics shown, but where I hunt, I don't need to get much higher.
Most of the time, I just find a big tree and sit against it at ground level, and I have just taken a folding chair out and sat in it instead of on the wet ground. Most of the ground I hunt is rolling hills/pasture/crop fields, so it works pretty well, too.
