Below you can find some useful links to organize activities and buy tickets.
Guided tours
https://www.associazioneculturalecalipso.it/
https://www.radiciaps.it/eventi
Ticket booking
https://m.museivaticani.va/content/museivaticani-mobile/it/organizza-visita/tariffe-e-biglietti.html
https://www.museivaticani.va/content/museivaticani/it.html#lnav_info
https://www.getyourguide.it/?selectedTab=0a050aa1-8582-1114-8185-8234a49c0003
https://www.romapass.it/it/le-card/