Hi Eggy,
Here's a good article on how to make a buttermilk substitute. I don't know if the results using it in the homemade sour cream will be exactly the same, but it's worth a try.
Buttermilk SubstituteAlso, the shipping overseas is pricey, but you can order powdered buttermilk here:
American Spice at recipelink.comHappy Cooking,
Betsy
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