My set up is a c twist with mini protank. I like to switch flavors sometimes. Problem I'm having is I'm afraid to carry my spare protank in my pocket. I'm scared it will leak and ruin my pants. Does anyone have a suggestion for how to carry it. Ideally it will be not much bigger than the tank itself. I don't have room to carry a large case with me. I thought about using an old film canister but it's still a little Big for the mini protank.