Despite what is often written that it is pure cotton normally it is not. But I need pure cotton. I live in UK, England, Harlow. And I need it here. It can be through Internet-shop, or Amazon or Ebay. But I need make sure it is pure as one time I bought through ebay where was written it is pure in fact it was not.
I was going to suggest eBay as for some reason it's easier to find 100% cotton thread abroad. What I'd recommend is having a conversation with the seller prior to dispatch saying you only want 100% cotton thread and that your buy their product on the undertaking that it is what it says and, if not, you expect a full refund and you will leave negative feedback.
That's usually enough to make most eBayers know you mean business and they won't even try to send you something that won't satisfy you because it's not worth their while.