Rear light recommendations

Bwgan

Hi

I need to get a rear light that attaches to an aero seat post (C'dale Slice)
Can anyone recommend one the balances and stays put on the point of the seat tube with a long enough rubber strap, and that is bright?

Thanks in advance

LegendLust

This

http://www.wiggle.co.uk/exposure-flare-rear-light/

With this

http://www.wiggle.co.uk/exposure-saddle ... g-bracket/