I discovered that the lid from my Jetboil fits nicely on my Backcountry.com titanium 700 mL mug/pot. I should note that the lid I have is the standard black lid - I don't have one of those space-age Jetboils with color-changing action. Anyway, it fits a little loosely at regular temps but once the pot has some really hot liquid in it the lid snugs up quite well - never had any issues with spillage. It's perfect for changing the "pot" into a "mug". The Jetboil lid is admittedly a little beefy at around 1 oz, but I think it's worth it for the mug functionality it provides. I also made a reflectix cozy to make it in an insulated mug - I like my coffee as hot as possible.
The backcountry.com pot/mug, the cozy, and the Jetboil lid have a combined weight of 5.3 oz. I use some foil for a lid when actually boiling - don't want to risk melting/warping the Jetboil lid. All in all I've found it to be a great solo system.