CDS used to make a LOT of Colorado narrow gauge dry transfers in N. Almost anything you could want for D&RGW, and a few other roads. I used them on my "oldie" cars.
All of my Nn3 MT flatcars have stakes. They may have been made without them as well, but if so, I didn't buy any, and don't remember them.
As for the Z flatcar from Nelson Gray/MT, the best N scale use I found for it was to cut it in half lengthwise, widen it a little, add a wood deck, and make truck trailer. It makes a very nice short trailer behind a straight flatbed truck, or for a more modern layout, a "pup" to trail a longer trailer.