I got the Timbuk2 Command Messenger Bag (oxford nylon black in medium size) when I was in San Francisco back in December 2011. It was retailing for US$130 which after 8.75% California tax comes up to US$141.375 (S$176).
This bag is Transportation Security Administration (TSA) friendly in the US because the laptop compartment can be unzipped separately to flatten the bag for it to pass through the X-ray. In this way you do not need to take your laptop out from the bag. I have not tested this in Singapore Changi Airport yet, but my guess is that you still have to take the laptop out from your bag.
At that time when I got this bag, I am using a 15″ MacBook Pro and hence I bought the medium size, but now I am using a 13″ MacBook Air and this bag is way too big for me! I should have bought the small size instead.