Where can I try out and buy a Japanese rin gong in London?

Something like this:
http://www.samadhicushions.com/gongs.html?id=fNkMMpf2

Hi,
I thought these were more usually Tibetan or Chinese, let's say
Buddhist, so not just Japanese.  When I see these, it is usually in
stores selling Chinese or Tibetan artifacts, and also in stores
catering to the esoteric:  books, incense, beads, crystal balls, etc. 
You probably know the kind of stores I mean, and probably know where
to look.  I would almost bet that a couple could be found on
Portobello Road.