For you to get married in his country you need to apply at any normal Home Affairs for the letter/certificate it takes between 3 and 6 weeks. Then you need to go to Consular Service in Pretoria they will apostle takes 2 days ( place a seal on the letter).
There are private people who can apostle but I'm not sure if this would be acceptable. We have just done this for a friend getting married in Netherlands
If he gets married to you here he needs to have a valid permit even tourist visa is fine and he will need the same type of letter from his country. Its often called a letter of non impediment to marry.