Would cut up an old sweater of mine and sew it up the sides. Sebago Cove pattern by Alicia Plummer-$
Knitting pattern - The Ruston Cowl (The Velvet Acorn Designs)
Cove Cardigan knit pattern by Heidi May (back view). Classic Wool Worsted by Patons North America. Pattern in 5 sizes: 2/3, 4/5, 6/7, 8/9, 10/11 years. US size 8/5.0 mm, 420 - 710 yards / 384 - 649 m.