Is there another nursing baby available to help get your breasts stimulated?
When my cousin was going through a similar experience, I let her nurse my baby and that seemed to help more than all the pumps and drugs, kwim?
Yes, my baby had to go hungry for a few hours before she would latch onto my cousin, but, in the end it was worth it. Once her baby came home she was able to breastfeed for over a year!

We waited until two weeks before her baby was due, and then after the one day, she was able to keep her supply flowing with the breastpump.