Here's a very small tube bender, designed for use on 3mm hollow brass tube.
I needed this to fabricate a new choke tube for a Mikuni BT carburettor.

Additional parts required:

2 x M5 x 25 bolts
2 x M5 nuts
4 x washers

Instructions for use

1. Position the bender base and handle to roughly 90° and insert the tube between the two grooved forms.
2. Gently clamp the bender base and the tube in a vise, or just wrap some tape around the tube and base to hold them together
3. Rotate bender handle until the desired bend angle is formed.
   See photos for reference.