We've got in a new range of helmets from Park & Urban experts TSG - available in child, youth, and adult sizes. For now these are just available in store, not online... 
People often ask us what size helmet their child needs. Rather than going by age, we think it's best to measure your child's head (circumference just above the eyebrows) to get the best fit.
Using the TSG range to illustrate this,
The Nipper Mini is 48-51cm, $80, and we've got a Panda-themed one (as well as many others to order)
The Evolution Youth is 52-54cm, $70, and we've got matte orange in stock
The Evolution and Kraken are adult helmets, available in S/M (54-56cm) and L/XL (57-59cm), and come in all sorts of colours and cartoony designs.
(and if 59cm seems too tight, we recommend Urge helmets which are available up to 61cm)