But why would you want to? The G9, without any adapters will focus down to 1cm in macro mode. That's probably better and closer than the close up filters.
You could probably use those add on lenses that screw in like a filter, some people really dislike the quality of them, but that would be the only option on a G9. You can find them all over ebay, but maybe someone else can vouch for the quality of a particular brand.