Finally got 2 packs of backing soda, all the better because they sell the 0,5 LB (454 Gr.) only here (on the pictures they use a 1 LB package).
This stuff is only available at what we call "toko's and warung's" here, mostly Indonesian/Surinam shops for food. I called the one I remembered from my youth and they said, sure we got it. Drove up there today and they had like packets of 50 gr. each....sigh.....and not the Arm & Hammer brand either.
So I googled some others and the next one I found and called I was more lucky, he had the stuff that I described. Cost €1,95 per pack.
They're cheaper here, but the shipping costs kill the fun until I know if it actually works:
http://www.baking-soda.nl