In 1843 William Roberts translated a selection of the letters of Isidore of Pelusium into English, as part of his book A History of Letter Writing from the earliest period to the fifth century. I stumbled across a copy of the PDF which I must have downloaded ages ago, while looking around my hard disk for something to read during a period of no internet access. Isn’t Google Books wonderful? The book also contains letters of Phalaris, Cicero, Apollonius of Tyana, Synesius, and so forth. I will scan these and make them available in due course.