Crab Claw Herb from Vietnam

I recently received a Vietnamese cookbook that lists many herbs used in Vietnamese cooking. Are you familiar with an herb called "crab claw herb"? I have never heard of it and don't know where to look for it.

This is a wild herb called "rau cang cua" (Peperomia pellucida) that grows everywhere in Vietnam and is not cultivated usually. Here is a picture:

We do not have access to this herb. It is on our "wish list" to grow but we have not found it yet.
I should point out that there are some people who think it is what we call vietnamese coriander (Polygonum odoratum) but we do not believe that is the correct herb.