Warning - Redneck Repair
For less then $20 go to the hardware store and buy a shovel or like tool with a composite handle. Cut a section out of the handle 16 9/16" long and install it into the stock pro bumper brackets. Fits perfect! You will need the "standard" rmk rear bumper end caps to finish the job off since the "Pro" rear bumper end caps are different.
I happened to have a shovel with the composite handle that was broken right at the spade so I wasn't out anything except the end caps for the standard rmk. The standard rmk uses an aluminum bumper that it the same thickness at the composite tool handles. From what I've seen all the composite tool handles are 1 1/4" o.d. X 1/8" thick tubing for the most part. They are very easy to cut with a standard hacksaw and do so without freying. Cut, drill a few holes and mount in less then 1/2 hr.
You can find many different colors also. Reds, blues, greens, yellows, greys, etc....
In search of the color I wanted for next time I bought an extendable prunning saw (6' - 12') with a 6' section of the needed 1 1/4" o.d. tubing so now I have plenty of replacement rear bumpers and can prune a few trees for $29. lol