Chant notation for this version of Caelestis aulae nuntius (I Vespers SS Rosarii); or name that tune

I'm looking for chant notation of this version of Caelestis aulae nuntius. I cannot find this in the "usual" books. Can anyone tell me if this tune may be borrowed from another hymn so that I can find the notation?

https://youtu.be/ISoxbr8fnww