Make sure to get the newer 4 stroke models. The old 2 stroke are loud. When you are traversing unstable areas, you end up constantly using your feet to balance. Meaning immersion in mud. water, snow. Not a problem with an atv. You will be able to access more remote areas. Make sure to buy the single wheel cart that is built specifically for it by Rokon.
Do a craigslist nationwide search and you will find a few. There is also a rokon specific sale sight that will help you locate some.

Just for thought. There is an AWD motorcycle called the Christini, that functions similar to a Rokon. It is in use by Spec. Ops. units. Also not cheap.