What episode of the Hills are you talking about? Also where abouts in Material Girls did H Duff carry the bag, what scene do you remember?
EDIT: Ok I just had a quick glimpse at Materials Girls and I think the bag you are talking about is the one that H Duff carries just after she gets her engagement ring and they go to their company's office for a meeting?
It's a hobo bag with a dark tan coloured very wide shoulder leather strap that has two lines of gold studs on the strap - one at the left side and one at the right side. There are also two buckles on the strap - one at each section of the strap where the strap meets the bag itself. The bag then is a beige colour but is a little metallicy. It's a fab bag, would be interested to know who makes it myself!