LJ Brain Trust, I need your help

Okay, I'm wanting to make the costume that Isis wears in the DC comics series 52 Weeks.  To do this, I need to get some jewelry type pieces, but I don't know the name of the symbol.  I know it is part of the symbol for Isis in Egyptian hieroglyphs, but not the symbol itself.  What I'm looking for is the name of the piece worn on her necklace and circlet in this picture.  It looks like an open side up stylized horse-shoe with a jewel in it.  Anyone know what it's called?

I'm wanting to make the costume on the right for me.  It's one of the reasons I'm going to the gym now :)  Want to be able to wear it for Dragon Con IF I get to go this year.

So, does anyone know the name of the symbol?