I found the part I needed without difficulty and ordered it from an easily navigated website. It was delivered in a timely fashion.
Pad (aspen) for: 4000 dd/dm/sd/sm also -
Pad (aspen) for: 4000 dd/dm/sd/sm also - back - for: wc/wm42/47/45/49 (27 3/4 x 33 1/2) sold individually - limited stock o/s wh8ar
Buy this part and as many parts as you like and pay only $9.99 shipping, within the Contiguous United States.