Does anyone know what size o-ring to use for the fill screw on the kayfun Lite? Both of my K-Lites leak a little bit out of the fill fill (screws are tightened down well). I tried using o-rings off of the screwdriver that inTaste sent along with my first one, but they're a bit big. If anyone's already found a source for the correct size o-rings, a link to you source would be greatly appreciated. Thanks!