I've made cardboard cutouts before. I traced a pattern onto the cardboard and cut it out myself with the same tools I use to carve a pumpkin. It works great if they're willing to go for that look. It isn't the most realistic sleigh, though.
I bought a used model for a decent price, but I use it fairly often for wedding photos. If you pick up some more clients who want a sleigh photo, then it's worth looking for a used model. I made my money back fairly quickly. I know this might not apply to your situation, but I thought I'd throw it out there.