You can find lots of spendy items on the kubota web site, the Can Am RTV site, bombardier, Polaris, kawasaki, and many others in Europe. Most all the 2 wheel tractor implements like sweepers will work on your RTV BUUUUT they are hydraulic drive as a rule.
The issue is what you want to do with it and how much you can afford as most all of them are hydraulic drive.
One equipment seller has a hydraulic powered front snow blower with a hydraulic power pack in the dump box which requires the end user to run the pressure and return oil hoses under the RTV frame.
If you have a 2 inch receiver you can put a lot of implements on it but its a lot of money for a motorized rotary mower that will need auxillary hydraulics or a winch to lift it.
Does your mule have a winch in the front along with the hitch?
A lot of folks use RTV's to bale hay in Europe towing hay rakes, tedders, hay piler gatherers\ and round balers and you would be able to use inline square hay balers as well.
As far as fence line mowers your looking at a towed rotary or flail mower with a limit switch operated shielded disc mower.
and you may need a three point hitch on wheels like the ones used by the Amish and Mennonites for horse drawn implements to do this.
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