Hanging Bag off 190XDB for weight. What do I need for tripod?

I wanna hang my bag off my 190XDB to help weigh it down when it gets windy.

What do I need for my tripod? What's the tool called that goes in the middle arm of the tripod? I've seen people do it this way before...

My tripod has a hook screwed into the center column, while I don't know what you could do to the 190XDB, I assume you could simulate the same thing with a small length of rope with or without a hook from a hardware store.

This might help too? http://www.vistek.ca …to-166-utility-apron.aspx

fashion a hook from some stout wire