Where could i buy fleece from for my rats?

my rats have a wire meshed cage so at the top it has holes in, so i use old t shirts to cover it up, but since it is thin material it gets covered in holes pretty quickly. they have a hammock that is made from fleece which they've had for about 2 months and it doesnt have a single hole in it. i want to know if you can buy large sheets of fleece and if so where from. it needs to be somewhere in the UK.