I was a bit obsessed with Sichuan peppercorns a few years back..
If one wants to have a good introduction to them, Huang Fei Hong Spicy Peanuts are on Amazon and many asian grocers.. they consistently have fresh and numbing pods mixed in.
I've never got good numbing Sichuan peppercorns retail in the US, but have gotten some really strong ones off of Amazon.