Sequestrene is how you spell it - available on line, just google Sequestrene.

Bjorn - a word of advice - please delete your email address from your question. This site is open to the whole world and I'm sure you don't want to be inundated with spam or worse!!!

If you have trouble you can try using iron sulphate instead - works for me and much cheaper, though the iron isn't chelated as it is in sequestrene.(This makes it easier to be absorbed by the plants)