It is a modern circuit, Thus you can buy all components in the local store or buy KIT. And the important thing is the overcurrent protection.
This is how to modify old Lead-acid battery charger or convert power supply to battery charger in automatic. To protect over charging by CA723 and power SCR
Cheap adjustable 0-30V 3A Laboratory DC Power Supply. high efficiency regulator circuit by IC regulator UA723-TIP3055 as power.Protect over load maximum 3A