I need the ones that seal the center air tube above the coil head. Does anyone know a vendor selling these in, say, a 10-pack? Also, is anyone selling the (new) silicone replacement coil insulators? I've been rebuilding the heads I have, but the silicone parts are starting to get a little ragged. I suppose I could buy new heads, but the metal parts on the ones I have are still in great shape, and just need the rubber parts. Thanks in advance.