I used to have a pendant like that! Got it at a sea shell store in a coastal town. They are inexpensive.
Here is an eBay listing you may like to look at:
Natural Gold Plated Spiral Seashell Pendant | eBay
<p>Natural Gold Plated Spiral Seashell Pendant. </p><br /><p>Actual pendant on photos </p><p>Natural looking</p>www.ebay.com
There are lots of listings for gold /silver plated seashells on Etsy. Here is one example:
This item is unavailable - Etsy
Find the perfect handmade gift, vintage & on-trend clothes, unique jewelry, and more… lots more.www.etsy.com
Thank you!
Something like the pearly shell?