Stressed out mom

Hi, I'm a mom of a 14 month old boy and my son can only use your infasoy milk. It was the milk that saved me in that my son had colic and after trying so many different brands, the infasoy was the winner at the end. He does so well on it and it works well for him. With saying all that, it is so hard to get in Kwa-zulu Natal, Durban South africa. Dischem, clicks, pick n pay, game. I have tried them all and they all say it's a supplier issue. I've gotten the last 2 900g tins and I'm praying that the supplier issue gets sorted out before my son runs out. Why is it on produced in 900g tins and not larger ones? What do I do next?