TAG Flat Brushes
TAG No 12 brush for use with one strokes can be found here.
If your brush has got bent and out of shape try the following -
Put some boiling water in a mug and then pop your brush in. Run the brush alongside the mug as you raise it out of the water to keep the shape. Dry standing upright to retain the brush shape.
Apparently hair gel also helps re-shape brushes using the above method.