I have a Topeak OS rack with the lock and 3 Topeak bags (#4 is on the way by mail). I've looked at the Topeak Drybag on their website, can't find them in the stores yet, and it's still a possible future purchase. In the meantime, yesterday, I bought a set of InTransit small waterproof panniers. Now all I have to do is get up the courage to drop my laptop in the bag and see how well that works. GULP! Sounds like it's time for me to do another thread and poll.