Actually, a lady in my (Presbyterian) church wears a necklace that consists of a Star of David alongside a Christian fish symbol.
Oh, that's a great idea. I'll look for one of those.
I just found one online that is the Christian cross and the Star of David, so if the Christian gift store in town doesn't carry something, I'll order online.
My first thought on seeing someone wearing both is that they're a Messianic Jew.