I have made several pads like that; the rice is the lightest weight stuffing you can use except for oat or buckwheat hulls and I don't like the noise they make sloshing around. Use the rice; it's not that expensive and it lasts foreverl I don't see how you could get bugs when it is heated so often. Put it in a large zip bag to protect it if you must or drop it into a pillow case. It would seem that one heating would get rid of any eggs in the rice.