Parker was first asked to spar with Klitschko when training for his win over US journeyman Keith Thompson in Pennsylvania in August.
Trainer Kevin Barry said he was keen for Parker to train with Klitschko, who is the WBA, IBF and WBO champion, but it had to come with more notice.
"It obviously doesn't suit at the moment, when I've already got a four-week camp in Vegas," he said. "There's no way we're going to be flying over to Europe and back to Vegas and back down here [to New Zealand]. I'm going to end up getting two weeks' work.
"I want Joe to work with him because he is the measuring stick and I think it would be a huge growth thing. It would be a very good mental test for Joe to be with the elite of the elite." It could also serve to take away some of the mystique surrounding Klitschko should Parker eventually fight him.
For Parker, who took his perfect professional record to 11 victories with his comfortable points win over Sherman Williams in Waitakere last week, a title shot is still some way off due to not only his relative inexperience, but also to the difficulty his promoters are having in finding opponents for him.
No one in the top five of any of the associations is willing to fight him because of the threat he poses, preferring to play it safe in the hope of slowly moving their way up for a mandatory challenge.
The same goes for those ranked just outside the top five.
Duco has made offers to Fres Oquendo, Travis Kauffman and Australians Lucas Browne, Mark de Mori and Solomon Haumono, to no avail.
Maddalone, a tough-talking, aggressive fighter from Queens, New York, is close to being confirmed, but Parker should be far too classy.
The 40-year-old Maddalone has a 37-win, 8-loss, 1-draw record, but has been stopped twice by Brian Minto, whom Parker knocked out in July.
Maddalone has lost only one fight in his past six - to undefeated Englishman Tyson Fury. However, the much taller Fury had an easy time of it, with Maddalone repeatedly walking into his jab.
Barry said of Maddalone: "He's a heavy hitter, especially in the first couple of rounds. He's a tough guy. He's going to come forward and Joe is going to have to beat him down."