DVDs are cheap to buy, are a long lasting storage medium and can hold a large amount of data. Given this, it is surprising how few easy to use and streightforwward backup solutions which make use of DVD as storage media exist. Only few let you write directly to DVD, most need a two step process - create your backup on the PC and then burn it onto DVD.
This Ebay search for'Backup to DVD' only searches for the words in the title of the items. It is likely to only return a few results but these should be highly relevant to the search term.