Rio Grande has clear glass lockets so you can see without opening the locket. Unfortunately they don't have an online catalog.
I just called them - the locket I was thinking about it about $40 (item 694 221, without chain).
1.800.545.6566 - this is their number if you want a catalog. (it's free)
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Have you looked on Ebay? Or you might check out estate sales/yard sales in your area. I don't look at jewelry much, so I skip over that at the sales - but you might find it that way.
I am getting one of these for Alley's fur. The heart shaped one with the paw print. I was worried about a regular locket coming open and losing the fur since I only have one little bit of it.
It's huge, too, I expected it to be smaller so I'm not that happy there(I did kinda expect it to be this big).....but here's a pic I took of it next to my thumb for size comparison.