Sandy,
I think they are made or distributed by Southco. Best pricing I have gotten on Southco stuff is from boat manufacturers. I needed some Southco stuff for a Cape Horn and called them and they said they can sell it and ship it. Owner chose to change hinges out rather than pay the price.
I think it is spelled DZUS. Check this out:
http://www.southco.com/landingpages/dzus/
Let me know if you find out anything better.
Mick