Mums who are bfing when they return to work find that their supply adjusts to feeding less often on work days (generally mums express fewer times at work then they would feed at home). So I am sure it would be the same for you - if you express more often some days your supply should adjust accordingly.

I forget now what sort of pump you are using - are you double pumping? If not that might be an option for you to consider. Also I have heard of mums who have worked out how to pump hands free with certain types of maternity bras that hold the pump in place, so that might help you to get an extra pump or two in while you are doing other things.

I'll try and think of some other ideas for you too.