You know what that hat looks like? It looks like the sleeve of a sweater cut and stitched closed at the top. If you found a sweater with small enough sleeves, like a childs sweater, you could make it! Of course you'd need to add the tie for under his chin. But I'm sure the more talented people here will come up with better hats.
How big is his head? Can you measure around his head for us? Or even just measure the existing hat?

That picture is soo funny!!! LOL