If you are looking for a cheap solution, try aluminum. Here is an IMUSA 3 cup (~700ml) mug. Light and cheap. There are a ton of older posts about these if you look around. I have and use titanium, but aluminum works just as well for me. I just got one myself. Make yourself a lid out of heavy duty aluminum or a pie tin. They work great. Sorry I don't have a ti mug to offer!