I bought a Victorinox brand luggage lock for my Pro-Tector bag. I found it locally, but it

is readily available on-line.The important thing for me – since I am in the US – isfor it to be TSA approved. This means airport securitycan open the lock with a special key without having tocut the lock. (Hopefully they remember to re-lock it ifthey do inspect.)I originally thought I might need a chain to reachthrough the grommets. Much to my surprise, this modelhad a long enough wire shackle to fit through all of thegrommets and still lock.Just thread the cable through the grommets and lock it tight.