Double acting baking powder, where to buy ???

[livelong]

I am trying to buy some double acting baking powder to try to make some steam buns.

Could not find it anyway, not in supermarket, not in Chinese shops (they don?t know it). Where can I buy some double acting baking powder ?

? typical double action baking powder may have 12 % of MONOCALCIUM PHOSPHATE, 30 % of Sodium Bicarbonate, 23 % of Sodium Aluminum Sulfate, 35 % of Corn Starch.?

The main ingredient for double acting is Sodium Aluminum Sulfate. I tried to look for this substance in baking powder, but it is not there. Thus in NZ, we can only buy single acting powder.

Any suggestion except asking bakery shops ???

[BubbaGourmet]

Virtually ALL the baking powder here in the States IS double-acting. As far as NZ sources are concerned I can't really say...but you can get it on-line form kingarthurflour.com