Progresso now markets a Panko breadcrumb product, both plain and Italian flavored. I haven't seen it in my local markets, but they sent out "preview packages" a year or so ago. I enjoyed using it, and suggest you might ask about it, because if your store carries Progresso products, I'm guessing they may be able to order them.
I usually buy my Panko at a specialty store in Manhattan.
Hey! I just checked out the store's web site, and you can order the Panko Breadcrumbs here: Kalustyans.