I saw a Pin on Pinterest about DIY Muslim blankets (some of them like the Aden and Anais can go for $30+)
I made several types of blankets all using cotton Bubble gauze muslim from Joann's Fabric. You will need 1 1/4 yards per blanket (45x45 inches) I don't have a serger but that would be the easiest way to finish off the edges of the fabric or you can double roll and zig zag stitch the edges like I did. I dyed some blue and left some white.
Dyed Ombre blue (I dyed this by dunking the whole thing into the bucket of dye and then slowly pulling the blanket out every 5 minutes about 3 inches)
I sewed the all of these on a corner so that they would be visible when he was swaddled.