Come to think of it, D-sub connectors are already "D subminiature", but I don't think we've ever seen the larger ones. Maybe that's why?
But smaller ones do exist, and you can still buy them, though the lack of production leads to very high prices; just take a look at this listing on digikey: https://www.digikey.com/product-detail/en/molex/0836119006/WM2142-ND/1001287
There's also a "nano-D" size that we only just learned about that's even smaller and even more ridiculously priced: https://www.digikey.com/product-detail/en/itt-cannon-llc/NDD-21PBRTT/1003-3059-ND/9691580
-R