Goodwill...of course, I reuse blankets around here, that are getting tattered and torn a bit, for the critter children; I just cut them into 'smaller blankets'.
Anyway, going to a thrift store should find you tons of different blankets to choose from
Last year around this time I found severaly really nice soft kitty blankets at Petsmart for about $2.00 that were on sale!!!
Dollar Tree also has some really nice fleecy blankets in their baby isle- I probably have about 30 of them because I use them constantly for my foster animals
Are you just looking for fleece or fleece like material? If so you can also check fabric stores and walmart - they usually have fleece remnants. I have some for my cats, they love the thicker almost sheep coat looking pieces I have. The edges aren't sewn and the fleece has held up through several washings.
Though you may prefer bright colors or patterns - I suggest greys and tan-ish pieces as they hide fur better.
I picked up a couple of nice soft fleece blankets at ALCO (a discount store) for less than $5 apiece. Also check out yard sales. (Just don't get sidetracked buying all the other great stuff you see
Salvation Army, Goodwill, Thrift stores. Instead of getting a full size blanket, look for baby blankets - they are a lot softer and smaller size. You might not need to cut them up; or just cut them in half
I'd forgotten about this. I had an old fleece bathrobe that was wearing out that I cut into pieces. Two weeks before I got Shareena I took one of the little "blankets" to the woman who had her. She told me Shareena loved it, slept on it ( or under it) all the time. I assume the other kittens and momma cat also left their scents on it. Anyway, I think it made the transition easier bringing her to her new home with the familiar blanket.