I tried to categorize some realistic CB options, based on speculated asking fees I found online:
LCB:
10-20m: Strahinja Pavlovic, Facundo Medina, Jhon Lucumi
20-30m: Riccardo Calafiori, Alessandro Buongiorno, Lorenzo Pirola
30-40m: Piero Hincapie, David Hancko
40-50m: Willian Pacho, Goncalo Inacio
(over 50m: Jarrad Branthwaite, Alessandro Bastoni, Jorrel Hato, Castello Lukeba, Murillo)
RCB:
10-20m: Aaron Anselmino, Oumar Solet
20-30m: Kevin Danso, Lutsharel Geertruida, Maxence Lacroix
40-50m: Ousmane Diomande, Matthijs De Ligt, Kim Min-Jae, Odilon Kossonou, Gleison Bremer, (Giorgio Scalvini)
50-60m: Antonio Silva, Edmond Tapsoba, Marc Guehi, Mohamed Simakan
I would suggest that spending 65m max for two CBs would make much more sense than splashing it on Guehi or Branthwaite.
It could be something like Diomande + Pavlovic or Calafiori + Danso.
Personally I would hijack Anselmino from Chelsea as well but that could be made through Lausanne (they buy him and loan him to Nice directly, if that's possible).