Where to buy Laterite (Duplarit k)?

Hello All,
I have searched far and wide for Duplarit K (in the US) and cant find
anyone who sells it. Do you have any suggestions where i could buy
this or any substitutes? I have used Dupla before with spectacular
results. The tank had so many plants that i started trading them for
fish at the local aquarium store :)

Thanks
nitin