Hello MG Hoosier,
you have not mentioned if you have a winch for your ATV Mule or if it is possible to mount on on the frame,
The Erskine front mounted 3 blade trail mower is powered by a hydraulic motor which requires a power pack that is put in the rear box of the UTV.
You can find these tow behind mowers at mowers direct, acre ease, swisher, dirty handtools, northern tool etc.
It would take a lot of welding to convert them to front mount if you really want to have a front mount trail mower with a side discharge.
The big issue for you is the amount of traction/adhesion you will need to operate the mower and if you have an area that is very hard to mow it may be worth your while to invest in weed fabric and weed fabric staples to cover the area and still let moisture penetrate the ground.
Even if you are able to mow this area you may end up needing a portable winch with a winch cradle which mounts in a 2 inch receiver on the rear to pull the atv and mower out.