Planet Bike Seat Leash - Bike Lock

Bike security is not too much of a concern for me.  
My riding does not have me leaving my bike out of my sight very often.   If I do leave my bike only when I run into restaurant or grocery store while touring or training.   I do not want to carry a heavy lock or cable but wanted something that would, as the say, "keep honest people honest" .   My thought was just to have something that would keep the bike from 'rolling away'.  

For the past two years I have been using Planet Bike's Seat Leash for my security.   It is lightweight and easy to carry.  I can lock the frame to a secure item or just loop the cable through the rear wheel and bike frame.   So far I have had no issues.... but then again, I do not use this for real "security" .

Here are a couple of images of the Seat Leash.

The seat leash with lock coiled up and easily attached to the Acorn Bag is pictured below.  

Perhaps this may be a solution that you can use.