You probably want to start with a not too expensive cage because it usually takes a few attempts to get a cage that is comfortable for long term wear.
You need to measure him very carefully when he is flaccid. Ball trap devices ( where there is a ring that goes around his scrotum with a method of attaching the cage) are the basic devices. More secure are cages with a prong that goes through a PA piercing, these are fairly impossible to remove with out the key. But you would have to have him pierced first, assuming he is not already pierced.
A plastic or resin cage is much lighter than a stainless steel cage but stainless steel is much easier to keep clean whereas resin or plastic cages need to be removed every few days to be properly washed. He should remove all his genital and pubic hair to avoid hairs being trapped in the device.
So yes, as @
Disciplined Boyfriend says, it will depend on how serious he is about enjoying the frustrations of being locked up and how much you want to make sure he does not play with himself when you are not there. That will help you decide on how escape proof the cage needs to be.