I just googled and this is one of the results that came up…
I have never used ebid (where this is being sold) so can’t tell you anything about it.
Another popped up on Etsy…but it seems to be a postcard sized photo…not necessarily a proper postcard with the marked up back…
I feel like I’ve seen another somewhere…but who knows where! 
Thanks for looking that up. I was just curious.
Well, I didn’t realize I already have many royalties cards from different countries. I love history. Here are some of them. I still have many other ancient royalties painting cards that weren’t organized…
Started from my own country
Empress Dowager Cixi of Qing Dynasty in China
It’s quite hard to find royalty postcard in China, not to mention royalty stamp. I found this in a set of vintage photo cards.
The last Emperor and Empress of Russia
Empress Sisi of Austria
King Louis XIV and queen Marie Antoinette of France
Queen Elizabeth II
I’ve sent these:
I sent this postcard of King Henry VIII:
Charles and Camilla:
Queen Elizabeth:
And Prince William:
I’ve sent a few Austrian Royals.
Emperor Francis II
Sissi
Crown Prince Rudolf of Austria
Empress Maria Theresia
Empress Sissi and her husband Emperor Franz Josef I
Ooo, Id love a Harry and Meghan card! I assume they are sold in the tourist shops. Wonder if anyone has received one?
Postcards I have sent of Queen Elizabeth II:
The Queen when she was older:
Two of the Andy Warhol images:
I have also received Empress Elisabeth of Austria:
And Queen Mary of Denmark:
I have sent a couple of Queen Elizabeth II
and
Well… I have this atypical one of the Dutch Royals with a Matrix-vibe. 
It was not a reall movie unfortunately. It shows princess Maxima, prins Willem-Alexander and Queen Beatrix.
Another one from the same company with just prins Willem-Alexander:
A regular picture of the prince and princess:
