1) Gaiwans are fun and can be used for tons of things, but require a certain amount of finesse. Expect dropage and burnt fingers at first. The largest you'll find is usually about 6 oz...which can seem small if you're used to mugs.
2) Kyusus are fun, but the better ones are unglazed. While the clay is usually less porous than, say, yixing...you might want to dedicate it to "just sencha" or something. Kyusus can be larger...but a 10 oz one will likely give you a nice mugfull.
3) Brew baskets are fun, versatile, and fairly idiot-proof. I don't know the size that came in Adagio's pot, but I buy a lot of cheap brewbaskets through Zensuke
. They currently have ones 3 1/4"
and 3 5/16
" in diameter. They used to have a TON of other sizes...I wonder where they all got to? At any rate, those two sizes are fairly common mug sizes. Just grab a ruler and try to figure out what the size of your mug is. Upton
has a few similar brew baskets on their site too.