Great answers so far! I ditto the fenugrek and pumping the lazy breast after she eats.
I have a 5 1/2 month old (3rd child) and work 6 a.m-11 a.m M-F. I also have one breast which produces less than the other (which is pretty normal and most people have a dominant breast). My girl actually sleeps in in the morning until 9, so to avoid pumping at work (which is soooo not fun or easy to do) I get up early, take a shower (easier than cold start pumping) and pump both breasts before going to work and then feed her when I get home. You produce more milk in the morning. You could try pumping one breast before you feed your babe in the morning, then continue with your normal pumping routine that you have, it will give him more milk during the day and "demand" more from your breasts and increase your supply. I also recommend letting him feed as often as he wants in the evenings and on weekends and going straight breast (no bottles) for him all weekend. His eating will tell your body how much to produce.
One extra caveat - with my first two I worked from home and didn't need to pump as often, but when I did I found it got much more difficult to pump after 6 months. Your supply will naturally drop as other foods are introduced to their diets and it will get harder to pump. But, as foods became more of a staple, my kids dropped to only needing around 5 nursings a day and only the morning and evening ones were long, the midday feedings became shorter and shorter. So if you are able to straight nurse 4 times a day (morning, lunch, home from work and before bed) don't fret too much what little extra you pump at work is probably enough. And by the way, kudos to you for keeping up with pumping so long, I know it is not easy!