I just googled and found several symbols for you. Here is the site:
http://www.makesplash.com/
You have to go down quite a bit and look for a post called "Loosing my religion." Despite the use of the wrong word, it is illustrated by a nice little graphic, with 9 or 10 other religions and a couple of symbols of both Judaism and Christianity. This sort of reminds me of one year when I was in a newsroom and decided to do a small tree. There were several Jewish reporters concerned, so we compromised. The vast majority of the ornaments were small photos of section pages in the newspaper over the previous year. We also added a few dreidels and gold coins to balance out the red and green. It was a popular tree and lots of the ornaments got taken as souvenirs before the holiday ended.