This was an interesting conversion, taking a Yamaha Raptor ATV and turning it into a UTV. According to the article by Dirt Wheels Magazine, this was a kit that could be purchased, but apparently it is no longer available. A mini rally car skin was once available as well.
If nothing else, it provides some great photos that could help someone interesting in doing their own custom fabrication conversion. If you have the right tools and ability, this could certainly be a cheaper entry into UTV ownership. Albeit on a slightly smaller scale.
If a single seater is all you’re looking for, starting with an ATV rolling chassis could save quite a bit of fabrication work.