Make one. They aren't that difficult.

There are some disadvantages to camping in one though.

All that extra space means you cannot rely on body temperature to help keep the tent warm. This isn't a big deal, most people buy tents that are too big anyway and they aren't known for their insulation qualities. You will probably want to light a fire inside the yurt though and that is not only extremely dangerous, it is a great way to fill your tent with smoke. Some people use custom chimneys to mitigate the latter. Also, while it is technically portable, it is a lot of lumber and accessories to cart around. This is especially true if you want to fill it with amenities, like a stove, chimney, floor, and bed. With the amount of stuff some people haul around, a small camper/caravan starts to seem like a logical replacement.

So if you like to camp for a few weeks at a time, go for it.