How to keep up supply while pumping exclusively?

WBMom

I have to have a thyrogen stimulation thyroglobin test and a whole body scan which involved taking a very small dose of radioactive iodine.  Sounds worse than it is.  I checked with my Doctor, who consulted with another colleague, regarding breastfeeding.  My Doctors initial reaction was that I had to completely stop BF.  I was willing to do this for my health and the safety of my LO but I asked her to verify if I had to stop completely or if I could pump and dump.  After her consult she indicated that I can pump and dump for 7 days.  I need to start pumping on day 1 of the shot that I am given and pump for 5 days after taking the iodine, which has a very short half-life.  

 I pump 3 times a day at work now and do not make enough and have to supplement with formula.  Since I have to pump exclusively for 7 days - how do I keep up my supply?