I don't think it has to be exotic. Peppercorns should be easy. But any deviation from that (eg, maybe fresher) and often things start to become difficult.

As an example, I am always on the lookout for a type of shrimp paste that is common in South East Asia (Hae ko or petis udang). But I cannot find it in any asian supermarkets. I could order from Amazon, but then I am at the shell's mercy. I can find 10 other types of shrimp paste, but not this one. I've written to several manufacturers as I find it hard to believe that there isn't a market for it here, but no response from them.