The two in the center look to be belted plaid or phillamore or great kilt, (which are all the same thing) but without the ends being secured above the waist. There really isn't a shoulder strap with with them, other than in "Braveheart" and "Rob Roy" and a couple of other movies that got it all wrong. Rather, the ends are more often fastened together or secured to the shirt of jacket or both. Here, it appears that the two in the center just let them trail behind them.

I don't know about the guy on the right. Since the belt is on the outside of the fold rather than inside it, I am not sure what he is doing.

While there are some place that sell them, you could probably put one together yourself at a fraction of that cost. You just buy a 4 to 5 yard length of tartan, hem or fringe the ends where it has been cut (NOT the selveged sides) and fold the pleats in the back and put it on. If you use the search feature you can find several threads that describe how to do this. Some have links to sites that explain this in detail. Some sites even have videos showing you how. Then, after you have put it on, you just let the longer end hang down or tuck it in in the back, rather than pulling it up over your shoulder.