This is one of those pieces that you can add to your off-world outfit if you want that extra touch of detail. (Or if you're a giant nerd and have to have the necklace because you can)
The necklace eventually reaches the hands of Daniel Jackson.
I got mine as a gift so I don't know the exact details. But it was from ebay.com for around $150. It's solid metal but not heavy, and has metal ringlets around the entire length. There are also turquoise and dark brown beads. Not sure what the cord is, maybe leather?
They are somewhat rare at this point but you might be able to find one somewhere. Here's a few sites that might help:
stargateprops.com
stitchsloft.com has a ton of cool props/pieces for your outfit but may be too expensive- their pendant is going for $225
Some people are making their own! http://www.therpf.com/showthread.php?t=164621
I wish I could be of more help in this matter!
We also see the Eye of Ra with, well...Ra.
{WarriorClassStudios}