All good advice but the Bangor Ski Rack (or Ski Rack Sports as itis now called) is 100% for sure the way to go. I used to work there.
If you have any questions about Maine whitewater, feel free to drop me an email. I lived there for 27 years and I ran every whitewater river I've ever heard of there. Maine is a beautiful, mysterious place. Enjoy your time there.
ps. check out the book "let it rain". it's a good NE guidebook.