The most effective way to increase milk supply is to keep latching on your baby as often as possible.. However, since you are working this would be quite difficult. Otherwise it would be to express milk whenever you can because the more milk that is removed from the breast, the more milk you will make. It's all about demand and supply. Are you able to express at work?
Galactalogues like fenugreek do not work for every woman There are also others that you can take such as blessed thistle, brewers yeast, linseed meal, and oats, but again they dont't work for everyone. Worth a try though