Which Nenya ring is correct?

Which Nenya, ring of Galadriel is the "correct" one? I want to buy one to my girlfriend as an engagement ring. I mostly find this design:

However, I found it only made of silver - not suitable for an engagement ring. Then, I found this one here:

which is offered also in white gold version and also looks more like an engagement ring. However, it looks completely differently than the other Nenya I found.

How this is possible that there are two different "original" designs of Galadriel's ring over the internet? Should the other ring be also considered as Galadriel's ring? Any advice/information appreciated.