An alternative to downloading a copy of the play and then using the "find" function would be to read the play for yourself. This would involve you, the reader, doing the work instead of the computer, but more than likely you would be able to find the textual reference most applicable to your needs.
As a general rule, the best place to find quotations from anything is in the work itself.
The easiest way to find quotations about Polyneices is to download the etext of the play, then search through it using the "Find" function. That way you'll be able to find each time he is mentioned.