I found this forum when looking for exactly the same thing myself. I have a Sigg Metro Mug, which at about 8 ounces (.25 liters) seems to be the smallest mug per se. Very nice. Still, it's too big.
I looked around in laboratory equipment. They have what's called a Dewar flask, which is basically the ancestor to the Thermos. The bad news? $123 and up.
So now I'm thinking jerry-rig a test tube. You can get test-tubes in all kinds of sizes, with diffferent kinds of stoppers, and you'd only have to insulate them. A neoprene or silicone sleeve? High-density foam?
Saw this old post and thought I'd add a bit too it. Here in Australia there's some specialty coffee shops that sell Espresso travel mugs, I there's some places online that sell them as well from time to time so you might want to try that as well. But I don't know where you're from, so not sure if this info helps.
Symbols: = New Posts since your last visit = No New Posts since last visit = Newest post
Forum Rules: No profanity, illegal acts or personal attacks will be tolerated in these discussion boards. No commercial posting of any nature will be tolerated; only private sales by private individuals, in the "Buy and Sell" forum. No cross posting allowed - do not post your topic to more than one forum, nor repost a topic to the same forum. Who Can Read The Forum? Anyone can read posts in these discussion boards. Who Can Post New Topics? Any registered CoffeeGeek member can post new topics. Who Can Post Replies? Any registered CoffeeGeek member can post replies. Can Photos be posted? Anyone can post photos in their new topics or replies. Who can change or delete posts? Any CoffeeGeek member can edit their own posts. Only moderators can delete posts. Probationary Period: If you are a new signup for CoffeeGeek, you cannot promote, endorse, criticise or otherwise post an unsolicited endorsement for any company, product or service in your first five postings.