First pic is one of the O-clamps holding just a hook for small things.
Second pic isn't using the O-clamps but it could be O-clamps and when you have one clamp on the front ROPS and another at the back, you can hold long things down the side of your RTV.
It does block the passenger access but that's the way it goes.
In that 2nd pic, you can see the O-clamps being used to hold my homemade windshield in place.
The O-clamps are easy-on, easy-off so you can remove or move them whenever you like. I think I have 11 or 12 of them on my ROPS for holding just about everything.
Also pictured is a pic of the O-clamp itself. The handle on the lower right side of the pic is for attaching the clamp to the ROPS, the bolt with wing nut on the top left is what you can attach things to. The bolt pops right out so you can insert one of any length you need. I "think" it's a standard 3/8" bolt.
To buy them, they're available lots of places. I think I get mine from E-bay for about $5 each.