Basically I went with corn because it is supposed to stay hot longer, since it's bigger than the rice. It does smell a little popcorn-y, but that is fading each time I heat it up. I didn't put any herbs or oils in it because I read that the scent fades each time you heat it up and there is no way to renew it. 50# of screened corn was $7 at a local feed store and all the material was from my stash.
In it's pillow case:
Easy peasy lemon squeezy.