Where can I get some of the grommets that go on the bottom of the head? Not the silicone ones that slip on top of the 'flavor tube.' I need some of the white(ish) rubber ones that slip into the bottom and ground the negative wire. Of course, if the ones I find are made of silicone, that'd be even better! I ordered what I thought were the right ones from Kidney Puncher, but they don't fit. Anyone know who has them?