Hi!
This morning while looking at sparkfun new product, I noticed they sell some quite cheap motorfader ($19.95 for one, $17.96 for ten). I remember how hard it was for me to find some, so here’s the link:
http://www.sparkfun.com/products/10976
They have touch sensor 
But I don’t know if they work with MF_NG module?
Pilo