3 things that I can think of.
Your stuff doesn't look too heavy, so you may want to look for one of those bags that hangs off your seatpost like the detours Hightail. They only hold a few pounds, but when you get to work you remove the bag & there is only a small bracket left on your seatpost. There are other brands, but here's the link to the detours site http://www.detours.us/product_info.p...2he1dumin1cu10

I use a cage rocket (they look a little silly, but they are storage pods that fit in a water bottle cage). I can fit a flip phone, iphone, slim wallet, ipod nano & a few other small items in there. With a small seat bag for your repair tools, you should be able to get everything except for the food into the cage rocket (depending on the size of the wallet).

The other thing might be to bring your stuff in a fold up backpack like the Mountain Hardwear Scrambler. These bags fold up into one of their pockets and are very small. When you are riding home from work and your food is gone, you can fold the bag up into itself & stuff it into a pocket.

1 last thing, are there items you can make smaller or get rid of? (Slimline wallet, smaller phone, maybe a flash drive instead of a hard drive)