If you go to eBay and type a search for "CHARLIE CHAN LASER DISC," you will currently see that laser discs containing "Charlie Chan at the Opera" plus Charlie Chan in Paris," and "Charlie Chan at the wax Museum" plus "Charlie Chan in Rio" from Key Video are available. As you note, the other three films that are found in the VHS set are seemingly not to be found. However, I also found that six Monogram Chan movies are also available, through MGM, on laser disc: "Charlie Chan in the Secret Service," "The Chinese Cat," "The Jade Mask," "Meeting at Midnight" ("Black Magic"), "The Scarlet Clue," and "The Shanghai Cobra" (https://www.ebay.com/itm/The-Charlie-Chan-Collection-Laser-Disc-Boxed-Set-6-Detective-Movies-Sidney-Toler/133432469033?hash=item1f1131e629:g:JkcAAOSwgaVe3WKV).
Do you still view your laser disc Charlie Chan films? if so, it's been a long time since I have heard of anyone doing so!
Thank you for your post...it is an interesting question!