V.M.
Is there a local hospital or lactation center you could call for advice??
I don't have any answers for you. Try to stay on his schedule to keep your supply up.
If you could store enough here at home to get him through the week plus a little extra for emergency, then you might want to consider just pumping and dumping while you are over there, since when you come back you will be avaible to him.
No chance you could take him?
I whole heartedly think breast is best but i also want to "give you permission" if you need it that its really ok if you can't, you've given him a great head start already.
Wishing you a smooth trip
edit someone recdommended a hand pump for your luggage, great idea, I just wanted to mention that i ended up just expressing by hand,(basically massaging and sort of squeezing down) because i couldn't get the hang of the manuel pump. which ever way practice first at home. take care.