I experience the same issue with Aptamil Gold as they change formula, I have to call them up and ask for existing stock at NTUC as sudden change of milk formula might cause my baby to diarrhoea and rejections. You should call them up, instead and start to mix old and new version with a ration of 75% old and 25% new for your infant to adapt.
Not sure if there is a difference between Optipro and non Optipro but what I can confirm is Nan Optipro HA is now renamed as Nan Supremepro HA.