On that note, what I do is ask for Burpdogs or Trudy's treats. And that is what I send.
All this talk about overseas and the cost of postage has made me think (yeah, I know, scary ) that gift certificates are an option. It maybe not be as personal as you wish, but I would be happy to receive a GC to PetsMart from an overseas giver. And if I had an overseas givee I would find a place they like to shop or eat or a pet chain near where they live and send a GC.
And of course you can always get a GC from ebay and let the person have fun on ebay.