Platydoras costatus (also known as the Striped Dora, Talking Cafish, Humbug Catfish and Striped Raphael Catfish) are usually pretty easy to find.
Of the seven fish stores with 20 miles of me here in Suffolk, at least three will have them in stock at any one time.
I'd suggest you grab a yellow pages (or go to
http/www.yell.com ) and ring around your local stores.