If you are considering a Holga, then clearly medium format resolution is not the driving principle behind your decision. Not to be said on this forum, but methinks you should GoPro and be there.

But if that doesn't cut it, I'd hack together a very simple pinhole camera and expose on 4x5 sheet, or cut sections of 120 or 35mm roll film. You'll need a dark bag for loading the camera, but you won't worry a bit about sand and dust, and you'll get some photos with a style that works very well with Burning Man.