First off welcome to TBN.
Next you might get a better response if you post this over in the Attachments forum instead of parts/repairs.
And lastly - as a fellow who would love a Ditch / Bank mower of some type, I have done a lot of shopping and you can buy a LOT of flail for $9500 - is there a reason you're set on a rotary style cutter?
If you're doing something light duty or don't mow that often - a few users here have tried the Chinese Flails like Betstco, Farmers Helper, and Titan and reported good luck with them.
A 5' Light Duty can be had for around $2,200 - $2,900
65″ VL-AGL Gold Ditch Bank Flail Mower, VL-AGLC165 | Betstco
Titan 65" 3-Point Offset Flail Ditch Bank Mower
One point to note - even though they all come from China with the same Model Number (AGL-165 in this case) - they are NOT all made the same as they come from different factories / companies using the same basic design.
TBN User Jack Yuan is a great guy to contact about these mowers and which factories are taking shortcuts and which aren't. He will not give a Mfg opinion in open forum so you'll have to message him but he has several post over in the attachments forum if you start searching for Flail & titan you should find them.
Also TBN user Leonz is probably the closest thing to a Flail Guru that ever existed. He can likewise be found over in the attachments section on pretty much any thread dealing with Flail mowers.
Best of luck with whatever you decide to do. Be sure to post back here so folks like me can learn & benefit too.