I got one for my 30th birthday from a friend who's parents have a normal jewellery shop. She even let me choose between 3 models!
So maybe you are searching too far? Go and ask in any jewellery shop.
I also found some belly chains in the accessories sections of cheap clothes shops like H&M.
And now let me tell you that with a belly chain you will get a new range of admirers! You know, the kind of men who comes to you after your performance and tells you: "I was totally fascinated by your belly chain!"
Yes, I am not joking, this happened to me more than once!
MEISSOUN