I saw a photo of this once, and have seen quite recently at least one story describing its use, but have never been able to find a source for buying one:

A chain mail "bag" of sorts that is pulled tightly around the base of the penis and scrotum, and then locked. The bag is just large enough to stuff it when limp. Even partial arousal would be excruciating, as there is only so much space inside, ya know?

Has anyone else seen, or know of a source, for such a device?