Signing travel consent documents on behalf of father court ordered

I am a South African expat who is in NL with my son (turning 3). We have residency and have been here for nearly 2 years. I have a court order from South Africa that states the equivalent of The Sheriff of the Court can sign he parental approval documents on behalf of the father, should I not get the approval from him for what ever reason. I am travelling in 2 weeks to South Africa to visit family and for him to see his son, but he has still not given me ANY documentation "allowing" travel. I have spoken with a Dutch Notary who advised they cannot sign on his behalf, and do not know who can. Please PLEASE can you help and tell me who can sign on his behalf, or what needs to be done where I am not always in this situation. We have shared custody, but he lives 100% with me, and I make all decisions. The father has not paid any maintenance to date and has only had 4 calls with his son in 2 years. There is no follow up from him at all. What do i need to do in order for us to live our lives without requiring him. I will NEVER withhold my child from his father if he ever would be interested, but from a paperwork perspective I need to find a solution