Heres what I used last year. Please dont judge me lol.
For the base I used 2x6's for a frame. Then I cut a piece of 3/4" plywood to fit my front floorboard near perfect. I layed the cut 2x6's down first then screwed the 3/4" ply to it in the vehicle. Next I mounted a flag pole holder. For the stand itself I went to Goodwill and picked up a nice steel speaker stand for cheap. I cut the bottom off of it and jammed it in the pole holder, then filled what I could with some JB Weld. The speaker stand I used had a screw hole in the top of the pole. I purchase a piece of small channel iron from the scrap yard, drill a hole in it for the screw, then a couple more to bolt an aluminum laptop mount to it. The thing swiveled, telescoped, and angled. I feel it was pretty sturdy and didn't cost me no more than $30 total.
Since then I was lucky and found a Jeniko mount at Goodwill for $15. The thing was practically brand new. You would be surprised what you can find at your local thrift stores.