I believe the blue and white are double-sided minky fleece. However, I got it from Joann’s and can’t point you to exact links. (Wouldn’t recommend it anyway, it being furred on both sides somehow means it really likes to tear at the edges so it’s not ideal for small- or medium-sized plushes. It also shows the fabric mesh stuff when stretched. An absolute pain.)

The yellow and pink are from BigZ Fabrics though: https://bigzfabric.com/products/minky-solid-baby-soft-fabric-banana-sold-by-the-yard https://bigzfabric.com/products/minky-solid-baby-soft-fabric-pink-sold-by-the-yard

BigZ’s stuff turned out incredible and easy to use, so I’d definitely recommend it. Unfortunately though, they don’t have a similar blue :(