I had posted this in another thread but I found at my local Petsmart in the horse department, in clearance, for 7.99, the correct girth belt.
Here is the thing you have to look for unless you want to really work at dying it.
There were two versions of the same belt hanging together, both said Mohair but upon further inspection on the tag a few said (BLEND) those are the ones with a slight sheen to them and will be more difficult to dye.
The one I picked up is more cotton-ee looking and is a size 36 which is perfect for me the other 2 were size 50 and were made up of that blend.
Remember that in some pics of the real deal between the buckles the belt is held together with what looks like an elastic or canvas band so no matter what it will be a perfect fit.
Problem with the belt in the link above is that their smallest siize is a 38, woo! I weigh about 120lbs. I wear a size 30 pair of shorts. I'm guessing a 34 would probably be the largest possible one I could get. I do hear that they shrink during the dying process. I may purchase the belt and I can always trim it if I need it.