Two years ago I've made a video about password protecting your virtual tour. The challenge with that was that not everyone had the same server type (apache) and it was some ugly popup that wasn't customizable.
I've found this open source project which enables people to have a password protected html file, with some customization options to change colors and some texts. And you do not need a server, as this is decryption happening locally on the client side (locally) itself.
Security wise it's still not super strong, as most of the other files (media folder, js etc.) are still accessible if people have a bit of development knowledge, but this might already help a lot for most people who want to protect it in some easy way.