Its honestly draw of luck on these chargers...
I found one for an IPOD 1st GEN charger in the clearance bin for 99cents, and I've been using it for over a year now for my Diamond, NDS, etc...
try
www.dealextreme.com
I think they have some for about 2-3 dollars and come with free shipping. I'd order like 3-4 of them. When one dies chuck it and us a new one.
Chances are these chargers are pretty much the same, and belkin slapped their name on it, so they charge more.
But to answer your question, ANY charges that fits into the cigarette lighter, and has a USB on the other end will pretty much work on any Diamond.