Many people install a circular polarizer filter on the camera and leave it there. You will need a "Conversion Lens Adapter" (LA-DC58B) to hold the filter.

The Adapter will hold any 58mm filter.

However, you may want to look at the G6 camera that was introduced on Aug 19, 2004. The G5 is now out of production and replaced by the G6.

G6 preview can be seen here:

The adapter mentioned above will also fit on the new G6.