Well, a search of Google yields NOTHING for purchase.
There was this - http
/www.engadget.com/2007/08/31/jvc-announces-first-rewritable-single-sided-dual-layer-dvds/
However those disks don't exist. Also, notice the last line about "no shipping dates or details are available."
In the age of Bluray disks with 50GB of storage the need for DVD+RW DL is moot.
So, unless someone far better with searching than me can find a reliable retailer that has DVD+RW DL, I still contend that those disks don't exist.