Just bought mine from WingOn - Sheung Wan (basement). There are lots of choices there: 2/3 containers, round/square, with/without carry-on bag, etc, etc. Have yet to try this out. I got the one with 3 containers: 1 big round one for rice, and 2 smaller rectangle containers for meat/vegs/fruit. It comes with an insulated bag.
Or... if you already have your own containers, you can just buy the insulated bag. I got mine from Bumps To Babes. It's Allerhand. I'm very happy with it. It's got 2 separate compartments so you can separate hot (lunch) and cold foods (fruit).