I don't know if someone has made these or not. I would like plugs with an o-ring to insert into my tanks when not in use. Take the drip tip out and insert a small nubby plug with an o-ring like a drip tip. It would eliminate the extra length of a drip tip and make it easier to store in a travel pouch or pocket. I have some 35mm camera film cases that would be perfect to store loaded tanks but the drip tip makes them to long. Sell them in a 3 or 6 pack. I would buy them. I use an eGo zip case to carry around 4 to 6 tanks at a time and if I could eliminate the drip tips it would make them fit better. If you ever carry around multiple tanks how do you pack up your gear securely?