Well, it took awhile but I finally got around to buying a Superbumper. I'll use it when I don't have my bike hitch and bike attached.
On their website, they only have the Sparebumper which does not have a tow ball. The Superbumper has a two inch tow ball on top.
I called Superbumper and spoke with the owner Jeff Mohr. He had a few Superbumpers tucked away so I bought one of them in black.
Adolphus posted photos of his Sparebumper here.
https://sprinter-source.com/forum/showthread.php?t=69199&page=8
Mine looks the same except for the 2" tow ball on top. Although I don't tow anything, I think the tow ball adds a bit of height for more visibility and perhaps safety if it can catch a bumper. The rear doors easily clear the top of the tow ball.
The Superbumper is 24" wide with a 4" diameter bumper. The tow ball adds 3". It sits inward of the Superbumper edges. The Superbumper sticks out about 9" from the edge of the receiver (our Westfalia receiver sticks out beyond the plastic bumper).
Note: Discus has the Sprinter step bumper which he retrofitted and uses to carry a canopy tent. The step bumper extends out beyond the Sprinter.
https://sprinter-source.com/forum/showthread.php?t=33399&highlight=Step+bumper
https://sprinter-source.com/forum/showthread.php?t=37979&highlight=Step+bumper
I'll probably just mount a sewer hose carrier on the receiver as others have done to reduce the gap/space between the Sprinter bumper and Superbumper. (I don't have a spare tire.)
I used two of the rubber spacers (Superbumper has two fat outside springs). Each spacer is about 1/6 the width of an outside spring and much smaller in outside diameter.
There are four rubber springs inside the hitch tube.
The top of the 4" diameter tube has anti-skid mats so you can stand on it with care.
I'll probably add some reflective tape.