I think this might be of interest to you:
Long lasting, go anywhere 'gongfu' style 'teapot': Tuffy tea steeper + L200 Snow Peak "Stacking Mug" Double Wall Titanium(7.0 fl oz, 1.8 oz)
The double wall titanium keeps the tea hot but not the cup! The steam/liquid creates a complete liquid air tight seal while tea is brewing; no heat is lost while brewing in very cold temps! It took a few days for the new silicon smell/flavors to dissipate for the Tuffy tea steeper; initially my taste buds were repulsed and this teapot idea was a failure. But then, wait, the silicone taste went away and only the delicious raw green pu'erh taste remained!
I only mention the silicon taste in the beginning to make any other user aware that it did take 2-3 days for the taste to go away. Like myself, I did not want them to be discouraged.
There has been concern of the silicon as 'impure'. However, it is food grade silicone and from my understanding this is completely safe. I did quite a bit of reading from various sources(including wikipedia, scientific trial data, etc.) regarding food grade silicone; as a mindful person, I am very concerned. But, it appears very innate and safe.
Medical grade silicone has been impregnated into the body for life for many years, needless to mention breast implants.
As for as your concern as to the cost of an extra ounce, that is for you to decide while considering your priorities. I do more 'ultra-light' nomadic living. For me, this is much more feasible than shlepping a Yixing teapot, porcelain teapot, or a gaiwan for my daily tea.
Good luck! Thanks for allowing me to share this little combination with you.
Total cost, minus shipping: ~$25
What do you think?