calling all crafty people

My self assigned spring break project is going to be making my very own courrier style shoulder bag. I'm making my own patterns and I know exactly what I want, just not exactly what materials I should use to make it.

The basic idea is something that will be secure for traveling over the summer and next semester. It will carry my computer/electronics, so I'd like to use something that would be difficult to slash open. My original thought was getting a Pacsafe and incorporating it between the layers of the bag, but on further review this appears to be a) frikin expenisive, b) not guaranteed to be the right size (as the measurements are in liters rather than area) and c) would add extra weight.

My next thought was chicken wire, but that also seems like it would be very difficult to work with (aka I would come out with my hands in shreads and a lovely case of tetanus) and wouldn't be very flexible.

So I'm taking suggestions for something that is relatively lightweight and flexible, cheap, will provide some resistance in the event that the bag were slashed and can be cut (albeit with difficulty) to fit in between the inner and outer layers of the bag. I was thinking perhaps along the lines of a burlap potato sack?