Both open face and closed face helmets are acceptable.
Any of the motorcycle shops sell Snell-rated helmets and can order an SA or M rate helmet as can some of our tech centres. BOTH Snall M 2015 and Snell SA 2015 are acceptable. The debate around the difference in specifications has been raging forever.
Don’t buy any helmet without a try-on for fit and comfort. For that reason alone, I would not buy online.