Here is where you can buy one

http://www.flagandbanner.com/fab/produc ... id=HCULP35

And some Info

The Culpeper Don't Tread on Me Flag
The Culpeper Don't Tread On Me Flag reportedly was first used as the banner for a group of about one hundred minutemen in Culpeper County, VA who formed part of Colonel Patrick Henry's First Virginia Regiment of 1775. In October-November 1775, three hundred such minutemen, led by Colonel Stevens, assembled at Culpeper Court House and marched for Williamsburg. Their unusual dress alarmed the people as they marched through the country. The words "Liberty or Death" were in large white letters on the breast of their hunting shirts. They had bucks' tails in their hats and in their belts, tomahawks and scalping knives.

The rattlesnake device occurs on several Revolutionary War flags. The rattlesnake's eye, supposedly brighter than any other creature's and with no eyelids, is the symbol of vigilance. It is said that the snake never begins an attack, but once aroused it never surrenders. The snake was also portrayed with 13 rattles, symbolic of the 13 American colonies.

The photo at the above right (taken by Royce Culpepper) shows the Culpeper Minutemen flag flying in 1993 at the Holiday Inn in Philadelphia, near Christ Church where Benjamin Franklin is buried. It features a rattlesnake on a solid background above the warning, "Don't Tread On Me".