Not sure but I think I found it at maplin ( uk ), the 4051:
http://www.maplin.co.uk/module.aspx?ModuleNo=31820&doy=17m9#overview
So I could try to buy two directly from my local Maplin and try the thing before I order more online. 
Please could anyone could confirm that I am looking in the right direction :-/
If it works I am also going to try to use it with the "arduino as a capacitive sensor" ( http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1171076259 ). This technique is really great, the guy who done that is really good.
I imagine I would need two 4051, one for demultiplex and one for multiplex as the technique need two pin ( 1 input 1 output ) for each sensor.
Anyway if it works I will put the code and picts as a tutorials for people like me who doesn't know much about electronic.