As far as I know only from the publisher 321 studios.com or retail stores and distributors in the US.
Currently the reduced price is $99.99 to download or $99.99 plus a shipping charge for the actual software. If you're unlucky and HM Customs open your package, you will be charged VAT AND a post office clearance fee.
Of course, you can download a trial version. The trial version of DVD X Copy will allow you to make a partial backup of a movie, or whatever will fit on to one DVD. The trial version will expire 14 days after installation. TC.