This idea was shamelessly stolen from my co-worker, Tim (he, however, gives all credit to his wife Christine who bought him his lunch box).
I took my grandfather's old lunch
box and added a shoulder strap to it. The shoulder strap came from a
messenger bag that was given to me at a conference. The messenger bag
was covered in advertisements. Also, the lunch box has the advantage of
protecting my gadgets better than a soft sided messenger bag.

The lunch
box had a bent piece of wire in it designed to hold a thermos in the
top half of the lunch box. I don't need to carry around a thermos and
most of my gadgets are actually smaller than a thermos, so I wanted to
modify the wire to hold smaller items in the top half of the lunch box.
I grabbed two wire hangers and went cut out the long pieces. I then
tied the coat hanger pieces to the thermos-wire, used my glue gun to
secure the knots, and then zip tied the connections. The result is a
pretty manly looking man bag.
