"I'm 99% sure it's a done deal, and it's marvellous after 38 years' involvement to see things happen," Mr Glendinning, of Kingston, said.
Although the deal has been shrouded in secrecy, the mystery buyer is thought to be Blenheim vineyard owner David Bryce.
Repeated attempts to speak to Mr Bryce have been unsuccessful.
Closely involved with the railway's fate since operators Kingston Acquisitions Ltd went into receivership in November 2009 owing Prudential Mortgage $4.7 million, Mr Glendinning consulted receiver Lindsay McClean, Prudential and possible buyers to ensure the future of the once popular tourist attraction.
He said the receiver and new buyer were ironing out the last strands of the deal, and a public announcement would be made on Tuesday.
Boiler inspectors have been contacted, and on Tuesday Mr Glendinning will also fly to Wellington at the request of the new owner to get the appropriate licences for the locomotives from the New Zealand Transport Agency.
United States rail holdings company Railmark had been keenly involved in the bidding since mid-2009 and, on Wednesday, company chief executive B.
Allen Brown expressed his disappointment at losing the deal, which he said could have seen Kingston and Queenstown as a global tourist hub and centre for Railmark's international operations outside the US.
Mr Glendinning had consulted Mr Brown closely as potential buyers were considered and said: "It was a pity Railmark missed out on the deal. They would have been a really good buyer; that's what they do.
"But I think this new outfit will be just as good. The way they're going about it is very professional and, while they may not have the rail experience, they've got the business experience," Mr Glendinning said.
Meanwhile, the Kingston Flyer's longtime locomotive lobbyist Karl Barkley, of the Southern "F" Locomotive Trust, is busy with plans to get the vintage railway's Ab778 engine steaming again upon its return to the tracks.
Mr Barkley, of Invercargill, said the charitable trust wanted to work alongside the new owner to ensure the future of the 126-year-old railway and keep it in New Zealand hands.
He hoped to get a band of rail enthusiasts and Flyer supporters together, maybe as early as next week, to welcome the Ab778 back.
Even if the locomotive did not pass the boiler inspector's test, he hoped at least to wheel the Ab778 out of the yard where it has been languishing for the past two years and sidle it up next to a carriage for the occasion.
