To complete your San Gohan costume, you need his little hat.
Here is the pattern of the hat worn by Baby Gohan, in Dragonball. A sailor-inspired hat, with a ball (the Dragonball) on the top.
The procedure even includes 3 options for crafting the Dragonball.
Each of the models is available in 5 sizes
Several fabrics are suitable for this hat: cotton canvas, twill, duck, etc.
Those shown in the photos are in twill or duck, and the bias is in satin (more information on this in the procedure to follow).