Those charms on lobster clasps can be found anywhere at the moment (at least here in Germany). And they can be quite pricey depending on material and brand name.
Why spend a lot of money on those charms when you can make them on your own?
It is so simple - I almost didn't dare to post this how-to... And if this has already been posted, I am sorry, but I could not find it when I searched.
The costs depend on what materials you use, but my sterling silver clasp and my shell pearl are probably under 2 EUR.
The second charm was made from turquoise (or dyed howlite I think...) and I added some kind of frame by wrapping around some more silver wire.
First gather your materials and tools.
Pick one nice bigger bead or severals smaller ones.
Put your bead(s) on the headpin.
Now make a simple or a wrapped loop, just as you like.
I always make a wrapped loop, because it's more secure.
Then open your jump ring
(never forget: don't pull it out of shape, just bend sideways!)
Attach the clasp and the charm, then close the jump ring.
One more tip: you can also use old pendants and convert them to charms. Just remove the bail (often they can be bent open, sometimes you'll need a cutter or some other tool) and attach the clasp as shown in steps 4 and 5.
Of course you should only do this with quite small pendants...