It looks like the material is either sherpa fleece or microfleece. I tried to search for you and found some sellers but they are UK only.
Then I stumbled across this bed and thought it was interesting - also waterproof and sherpa fleece. It has a Tick tock pocket for the heartbeat clock and also a place for a hot water bottle to keep the puppies warm. Pretty neat! It is made by a company in West Yorkshire in the UK.
Puppy First Bed by Danish Design
This place ships to the US.
Danish Design Puppy Bed - Peticious.com - Delicious Pet Supplies -