My current Western Star does not need it as the spreader apron hangs out far enough to protect the pintle. However, on my previous International, I made one out of conveyor belt and just bolted it to the buck plate above the pintle. I used a piece of steel strap about 1 inch wide with 3 bolts to anchor it. Make sure it extends past the pintle about 4 inches, and is about 3 or 4 inches wider than the pintle on each side. Bolt it a couple of inches above the pintle and it will just lay in place. It worked well for me.
Hope this makes sense without a diagram.