For my rough and ready activities especially those outdoors I depend on my lanyards a really great deal. With it hanging around my next it can be tucked into my jacket, sweatshirt, or t-shirt and ride along in a safe spot. Its also more convenient then stopping to dig around in bags to locate the box with the setup, screw it all together - fill it up and find at that point everyone is ready to move on. As long as your not using a massive atomizer the battery will be the weighted end and you won't spill liquid down your chest and you can set it up and fill it up before you ever walk out the door. The only time you will spend messing with it while out and about is if you do need a refill before you get home.
The way I go as its cheaper then buying the ego cases and pretty much are like tey were made for e-cigs are the diabetese supply cases. I have several of these because they are available all over the place and are constructed to hold things that are much more fragile they an e-cig setup. These are available anywhere that sells diabetic supplies and testing supplies and certainly most drug stores and places like Target, Walmart etc. These cases are usually plastic or heavy duty fabric, essentially crush resistant, and inside have the net pouches and loops - normally for holding bottle of insulin and other equipment like glucose meters - which just happens to be about the same sizes as batteries and other parts of your set ups. the nice thing about these cases is they usually have some smaller loops that are used for syringes that do a great job for holding atomizers, clearomizers and/or cartomizers whatever you wish to have with you. Some of these can get pretty fancy and even have outside pouches if you want to keep a setup ready to go to grab out of the outside, side zippers and so on. Most come with some type of attachment device whether you want it on a belt, backpack and so on. Some also come with cooler backs and waterproof areas for keeping insulin cool - which will also keep your e-liquid from getting to warm if your out in hot weather. Not a good idea you use e-liquid that has been evaporated some so keeping it cool is a good idea. The pouch that holds the cold pack is waterproof so no risks to the battery- the chill won't hurt the battery.
One nice thing about going with the diabetic supply cases is because you can find them locally you are not guessing what will fit or not based on an online picture and short description - you can go look at them all and what the inside is set up with in your local store. You can also get these - especially the ones with more options - online like at amazon, online pharmacies sites, Google diabetic supplies.
I have gone through buying cases specifically made for e-cigs and found most don't have options for extra supplies and the configurations are not really versatile but planned to just hold the specific e-cig its made for. They usually cost twice what I can get a nice diabetes one for. And for the ladies out there - there are custom ones on amazon made in very pretty patterns and ost of options. Otherwise they usually come in colors like black, blue and now and then red.