rear light for trek madone 5.2

Bigdod

Hi
anyone have any suggestions for a seat post mounted rear light that would fit the unusual shaped Trek Madone seat post? I have a Knog on there just now but am conerned that the rubber band securing it is very stretched.
thanks

smegurmum

have you tried mounting it on the seat stays?

Cranks

Hows about this?

PK1

What about a saddle bag with a light fitting, such as a Toppeak mini