I am looking for a necklace type piece of jewelry for my wedding?

No, you could always get a pearl necklace though.

Try going into a fabric store or a craft store. Those women know everything under the sun!

http://www.tigerlillyjewelry.com/bridal_necklaces.html

try big rope pearls.

I believe the necklace style you are looking for is a lariat style. Here is one that you might like. I highly recommend this website. I ordered my jewelry from her for my wedding and I was very happy with it. You can customize almost all of the pieces on the site, so if you don’t see something that you really like it’s worth your time to send her an email. She was very helpful and willing to accommodate me – hopefully you will have good luck with her as well:
http://www.looneymaiden.com/store/agora.cgi?cart_id=2312237.528&p_id=CL-02&xm=on&ppinc=detail

I think what you’re thinking of is called a “backlace”.

Here are some sites to check out:
http://www.thebacklace.com/testimonials/
http://www.arnellas.com/backlaces.php

I’ve never used them, I just googled it, so hope you find a good place to buy this! I think they’re very unique and beautiful.

I think it’s called a lavalier