At first, I used a travel mug called the “Bubba Keg.” The label is long worn off, but I know it holds nearly 12 cups of liquid. It's also well insulated, so the tea stays warm for a long time. The main issue is its size. I'd rush out the door, tea bag tags trailing from the top of the 'Keg,' only to have no place to put it in my car. No way it would fit in even a super-sized cup holder.
For awhile a used a daintier version of the 'keg' that only held about 6 cups of tea. It fit in a cup holder, but the lid eventually cracked and it was time to move on. Those pretty ceramic mugs from the coffee shops barely held more than a single cup, plus I somehow would chip them just by looking at them. The plastic versions were slightly better, but they soon discolored and nothing would clean them. What was I to do?
Finally, I resorted to a mason jar. Yep, that's right, one of those jars you can peaches in. I picked up a lid that screwed on somewhere, I wish I could remember where so I could get some back-ups. A cup cozy, made for the larger size to-go cups and purchased from Etsy, kept my fingers safe from burns. Thus far, the old mason jar as provided the best travel mug for my tea, and I even think it's sorta of pretty when filled with my favorite brew.