These are showing up in a lot work outs, but my gym does not have the sled.  It may sound and look even worst but do you think pushing my truck in a parking lot would be the same ?  

thanks to those that respond.

My BJJ/MMA gym can't afford a prowler either, we use a Honda Ridgeline.  We modified a trailer hitch with a 2x2 steel bar welded on horizontally about 42 inches across, then welded two vertical bars at about 18 inches off center on each side.  This gives a variety of possible gripping points.  Part of what makes the prowler such a difficult exercise is the friction it creates on the surface so you do lose a little bit of that.  In order to increase weight (not for me), but our light-heavy and heavyweight guys, we just put people in the bed of the truck.

Make sure you have someone in the driver's seat, stupid point to make, but nothing surprises me these days