You could definitely go with the Hobb's Washable Wool. If that doesn't work out & you're looking for a higher loft cotton, I'd recommend Warm & Plush. It's available on a limited basis at JAF, but I can almost always find it online. I just bought a 90" x 25yd roll from
walmart.com because I love it so much (and it was a steal at $130 + free shipping). It is 50% fluffier than Warm & Natural/White, but every bit as warm & washing machine friendly. Cotton will definitely keep him warm on the coldest winter nights.