You could try scratchbuilding one. I built a GMC stepvan from sheet plastic card some time ago. It's not that hard, most of it is flat panels. for the curves use plastic tube, butt the sheet up to it, cover in filler, then rub down. For the dimensions, find a real one, measure in inches & build the model at 1mm to the inch, instant 1/24th scale (ish)
Pete