Re: racket grip
Since you mention that both of your hands doesn't fit the handle I assume that you're talking about length. What's your age? Anyway, you can buy new racquets with longer handles.
If you actually mean the grip SIZE (thickness), then you can add some size by using a replacementgrip and/or multiply/thicker overgrips. Altho an overgrip usually adds only 1/16 of an inch to the grip, so a using a replacement or buying a new racquet with increased grip size would be preferrable.