1. I brew the tea using a teapot then decant it into a thermos rather than into the cha hai.
2.I use a thermos with a tea leaf chamber like this one:

(this one has an extra cap on the bottom a feature that lets one stop the brewing even when carrying tea in a backpack on a bicycle.)
I've always thought of the thermos as a "step down" from drinking at home, but now and then I have had some experiences that have made me stop--

--and savor--
It has always been with oolong tea. Mostly of the aged variety.
Often after working at my desk at home I'll feel bad about wasting the leaves from the morning tea when it's time to go to work. I'll brew some more to go with me. The tea stays hot but sits much longer before I drink it. When I do drink it, new aromas and flavors are present. I think letting the tea rest for so long changes it.
In addition, often I have been at the library late and not brought and fresh tea, so I end up steeping something for much longer than normal. The tea thermos makes this possible I let it sit-- these are almost spent flavorless leaves mind you, on their 6th+ infusion (for oolong, puerh is another story) ... and lo-- a new experience!
For this reason I rank my thermos very high among my loved teaware. I also have a "yixing" thermos--

in its early days it did more harm than good, more of a novelty than an effective tea drinking tool... but now it can make cheap over-roasted grocery store oolongs taste much more subtle and lovely. I call it my "sea dyke magic thermos" -- so, it might not be popular but I think they are nice.
The steel doesn't agree with puerh though. For that there are the glass vessels:

My husband uses one like this at work, and works his leaves to death. He seems to enjoy racking up a large number of infusions as much as the tea itself.

At first I thought the glass would be more pure for my oolong teas. But the steel is better? Why would that be?
Have any of you discovered any great portable teaware lately?