Downloading Expansion section from lessons

Hi all

I'm off to sea for the next three months and wont have the internet available. I want to be able to download the expansion sections for each lesson because I find these really useful. I dont know how to download them automatically though as manually it would take a lifetime. I tried using wget but I dont want to download all the MP3 files, in part because I have all my planned ones downloaded, and I suspect it would put a huge strain on the server.

Could anybody help me with my predicament?

Thank you