I use nice, thick, waterproof "underpads" - on top of which I then place the disposable pee pads.
You can also use the underpad as the peepad itself - you just buy a few, wash them when soiled alot, rotate them through. Better for the environment, if it's realistic for you.
Check these out:
http://www.dog-bows.com/cgi-bin/TheF...436&category=1 http://www.personallypaws.com/
Ann