Westin or someone does make those shorty step tube inserts but they don't protect the entire width of the rear.
I have one on my truck now that I fabricated. When camping season ends I switch to an aux bumper that fits into the 2" receiver. A visit to the steel yard and $10 got me 2'x3" thickwall box tubing cut to my required length. I cut/shaped metal end caps, filled it with sand (for extra weight) and welded them in place. Then I welded it to the underside of a ball mount just behind where the ball/nut attaches. The ball mount is inserted upsidedown for two reasons:
1) uninteruppted step to better access the bed
2) a tow chain hook fits perfectly around the ball's shank & won't fall off
Now, I wouldn't go yanking really stuck vehicles using the tow hitch but for light jobs it's fine. I placed a stair tread strip on the top of the steel tube for traction. Runs entire length of the truck's bumper and keeps dorks from tapping the back end in parking lots. Also hits a snowpile before the bumper would, further protecting the aux. reverse lamp underneath. The drop of the ball mount places the aux bumper just at the bottom of the factory bumper which is perfect, since the ¾t Rams sit high as it is. To prevent side-to-side wobbling that normally occurs in a 2" receiver, the bottom of the 2" receiver tube is drilled & tapped for a 5/8" hex bolt. That cinches things tightly. Just remember to apply some grease or "never seize" to the ball mount's shank and that cinch bolt to prevent winter corrosion from removing it come Spring.
I've toyed with the idea of drilling an end cap, pour out the sand, and thread in a Schrader valve to create a handy "air tank" aboard. Although, I don't think the volume would hold much for topping off the big tires!