One of my favorites as well! I had a poke around and it seems there's a downloadable archive of it, though at "only" 500MB I'm not sure how complete it is: https://archive.org/details/X2ftpArchive
There's a mirror available at ftp://foto.lu.lv/pub/mirror/x2ftp/msdos/programming. Only via FTP, as far as I can tell. It works well with e.g. Filezilla. Log in as anonymous...