I discovered this when answering a recent fan's email.
I'm not sure when it disappeared from Sony's site. It used to be that Sony linked directly to the Amazon page, which is how I ordered my official set https://www.amazon.com/dp/B01M5ISEPY. Now Amazon lists it as an audio CD (!) starting at the low low low price of $70.32.
The Internet Archive's Wayback Machine has the DVD set on Amazon as of May 14, 2017 http://tinyurl.com/y694q3mv.
According to this site http://tinyurl.com/y2vdz2md the official release date was Tue, April 3, 2012. (Curiously, Amazon has listed the release date as Sun, April 15, 2012 https://www.amazon.com/Starman-Complete-Robert-Hayes/dp/B007G8SEF2 and Mon, April 16, 2012 https://web.archive.org/web/20170514070555/https://www.amazon.com/Starman-Complete-Robert-Hayes/dp/B007G8SEF2 .)
Places online which seem to have it still in stock that I will be passing on to the fan who recently contacted us:
Best Buy https://www.bestbuy.com/site/starman-the-complete-series-5-discs-dvd/20431492.p $29.99 plus shipping
Walmart https://www.walmart.com/ip/Starman-The-Complete-Series-DVD/20595542 $32.47 plus shipping
Barnes & Noble https://www.barnesandnoble.com/w/dvd-starman-the-complete-series/24893491?ean=0043396400559 $35.99 free shipping