Simon has lived with his mother since he asked to be with her eight years ago. His family say his condition has deteriorated and he has a poor quality of life.
Mr Donaldson, who has lived in Indonesia since the mid-1970s, said his ex-wife had demanded the equivalent of at least $6 million - the amount she sought during their divorce - before she would hand over their son.
Last month, Mr Donaldson and his eldest son, Alexander, travelled to Surabaya in East Java in a bid to fetch Simon with the help of local immigration officials.
Because Simon is the child of a foreigner, he assumed his father's nationality under Indonesian law, and authorities have the right to deport him to New Zealand.
Ms Yuhanie allowed the immigration officials and Alexander to see Simon and take photographs which show him chained by his wrist to his bed.
Mr Donaldson said his former wife believed Simon and Robin were the victims of magic "and somehow it has something to do with me".
"And as the sickness is generated by magic it will take magic to fix it. It is obviously my fault and I should pay for it."
At last month's meeting she demanded the equivalent of more than $6 million, as a "starting point" before she would allow Simon to leave.
Mr Donaldson said he made another attempt to fetch Simon last week but despite support from New Zealand embassy officials and local police he was again blocked.
Mr Donaldson said New Zealand officials had tried to get Simon released "but have just been getting the run around by the Indonesian authorities".
"They have informed Interpol and are taking it to the justice ministry."
Simon's sister Joanna, who lives in Melbourne, told the Herald she was shocked when she saw the photos of her brother chained up, and called for Mr Key step in and get him freed.
"When I saw the photo, I said 'that's it, no way'. I know he needs better care that is definitely not available in Indonesia."
Her mother had told her Simon, who is wheelchair-bound, was chained because he "lashes out" at her.
Ms Donaldson said her mother believed Simon's condition was a result of magic, even though it was diagnosed through medical tests.
"But she doesn't want to believe that. She's quite adamant that this is some sort of black magic. She's really making it difficult."
Simon's older brother Robin held a part-time job for several years until he took a turn for the worse. He is now living at a New Plymouth rest home and his father says he is improving mentally and physically.
"It is my intention that Simon join him there," he said.
New Zealand's Ambassador to Jakarta, David Taylor, said embassy staff had been in contact with the family and were working with authorities to find a solution.
Prime Minister John Key said the issue had been raised by Ambassador David Taylor with two Indonesian ministers, including Trade Minister, in Mr Key's presence on Sunday.
The Prime Minister said he wouldn't be raising the issue when he met with Indonesia's president Susilo Bambang Yudhoyono later today as he said that was not the appropriate level at which it should be discussed.
A spokeswoman for Mr Key said yesterday that the Prime Minister sympathised with the young man's plight.
Ms Yuhanie refused to answer questions about her son yesterday, directing inquiries to her lawyer.
"You can't force me. I am the victim too, you know. I'm not ready yet. You cannot just ask me now. Don't rush me."
