It seems not to exist. You can normally get the latest one (even if there's no link to it from the Prospect magazine) by simply changing the date in the URL for the previous one. However that's only producing a 'page not found message' at the moment, which strongly suggests that the October crossword has never been uploaded to the website.
Sorry!
(BTW: If you're really bored, and you've not done them previously, a few of the non-cryptic crosswords I've set myself for friends and fellow ABers are still available on line. Link on request!)