I did it a bit of Googling and maybe something like this:
http://www.amazon.co.uk/Duragadget-1.../dp/B000UUQGEY

It says earphone though so I'm not sure if it'll be able to record.

Or perhaps this USB Soundcard
http://www.htfr.com/more-info/MR237038

Not sure if it'll produce mono recording also though.

This looks more like what you're looking for but kind of expensive

http://www.cablesdirect.com/search_i...Keyword=USB-AV

Or this
http://www.spygadgetonline.ca/produc...roducts_id=192

Hope it helps!