My golden puffer is about 9"
They get big, as do most puffers.
Golden puffers can be hard to find, The store I purchased mine from has been open for about 7 years now, and they put a golden puffer on every order so far they have only had 2 in the 7 years, I was lucky to get one.
I would think if you look hard enough you could find a small one, but it will grow!
The valintini puffer might be a better match if your looking for a puffer that dont get big, but they are not gold in color.