Spring dampers for running gear hitch

[TooCents]

Recently saw a photo of spring dampers used inside the pole of a used M&W 9T running gear. I’d like to replicate this in the pole hitch on my running gear to dampen the jerkiness of a dump wagon loaded with gravel. Can’t seem to find anything like it for sale.
Anyone have thoughts on where to source these? Or even find something with similar use that could be used?

 

[RayIN]

I know of a hitch receiver for a vehicle with springs inside.
Your picture is a first for me, and appears to be a great idea.