I feel your pain! PetCo does sell the pads with the tray for a reasonable price if you have one by you.
PETCO Training Pads & Tray Combo Pack at PETCO
I haven't tried it since my little one doesn't move the pad around. I just got my almost 6 month old lil gal Fiona a week ago. When i am at work she goes on the pee on the pad but I can't reward her. She won't poo on the pad, that can be anywhere. But when I am home I take her out at scheduled times and she will go out side. My problem in the morning. The first 2 mornings I placed her on the pad and she went. I praised her and gave her a special treat that she only gets when she goes on the pad. She would go within a few minutes so I thought this is the way we'll do it since I would never make it down the 2 flights stairs and out of my apt, building in time for her to go outside. The last 3 mornings though...she has sat there for 30 minutes on the pad and nothing. The SECOND I turn or blink too long she is off the pad and peeing on the floor. I just don't know what to do.
Tomorrow I am going to wake up and take her outside see if that helps. I do use natures miracle no more marking clean up but at this point I should just wash the floor with it and really I hate the smell of the stuff.