I think the cheapest place to find them would be your local goodwill/salvationarmy/thriftshop!
I was lucky one day and found a whole bunch of fabric remnants of great quality fleece at my local thrift ship ON THE DAY THEY WERE HALF OFF!
Also, I would check our your local Joann Fabrics, Micheals, or Pat Catans. They also sell fabric remnants (the end of the roll, hehe. Wish they kept that nice big cardboard roll for us bunny owners too! Ha!) Or you can select your own patterns.
My Jake also likes to dig and I find that with his trimmed nails (thank the Lord for the vet, hehe!) that he does not damage to digging on my own bed (especially my fleece pillows).
Also, I’m sure you already know about this, but “digging boxes” filled with newspaper of inkless paper (I’m lucky because I work at a daycare and we get rolls of natural paper that is safe should a baby eat it!) are fantastic.
P.S: I’m new here and your Peanut is so, so cute! What a beautiful bun.