The original bike you were looking at, the Trek 2.3, has eyelets on it. That can easily handle your needs. If you must have the Madone then you can what twilkins9076 suggested in his link.

Personally, I've been commuting on 2 road bikes without eyelets therefore I had to carry a backpack. That got old pretty quick and found another solution. I bought one of those 5 gallon plastic containers that can be locked and left it in my cubicle. I used that container to store 5 days worth of clothes in: shirts, undies, socks and pants. I'll ride Monday morning with a back pack full of a weeks worth of clothes. Then I ride without a backpack for the rest of the week except for the leg home on Fridays when I have to take my backpack full of dirty clothes home.

I did this for a few months until I found a locker. Now nothing stays in my cubicle but the concept is still the same.