Kind of plain jane, but it works pretty well. I have a 2L Flask on order.
I used a 110V fan and a plug-in dimmer. I have a really good electronics store locally and the staff are guys that generally know their stuff. One of the guys I've had help me before recommended that I use a 110V fan and a dimmer so I didn't have to worry about losing torque at the lower speeds. Of course, it's high voltage, so you have to be a bit more careful. Seems to work pretty well. Spins a 2-inch bar really well. I have 2 neodymium magnets hot glued to the fan with opposite poles facing up. I have to admit, though, I expected a lot more torque with the 110V fan.
Here's the inline dimmer (don't buy it here... I paid less than half):
I just pulled the guts out and mounted them in the case.
Pay no attention to those loose screws: