I've got a bunch of drip tips that seem to fit some of my atomizers and cartomizers but are too small for others...they stick to my lip after the hit and then fall off and roll away, often under the couch. They are 510s if it matters. I seem to recall reading in another thread somewhere that you can just put a different O-ring on them to make them fit. Where do I go to find thicker, presumably heat-resistant O-rings?