Full custody over an Illegitimate child to acquire visa

So glad to find your answers that are so helpful. Can i ask something too? I am the mother of illegitimate child now aged 10yo. I have never asked for full custody but as i understand from your answers i have already this right. At present i need to apply for a visa for my son and i m asked to bring an official paper stating that i have full custody. Please let me know where can i get such an official paper? Do i need to get a lawyer, go to court for it (and "win" the full custody) etc. or there is a bureau i can just apply and get the paper i need within a day or 2?? Thx in advance attyLLL be blessed!

answered your other post