The Parkhead boss parted company with the Scottish champions on Thursday after four years in charge.
But his agent Martin Reilly said that while the 42-year-old was looking for a new challenge, he had "nothing lined up".
However, retired Hoops number one Bonner - whose 642 appearances is a record for a Celtic goalkeeper - scoffed at that suggestion.
"I am sure he has something lined up," the former Ireland international told TalkSport. "When you are winning things in Champions League you are hot property.
"I would be shocked if he left without having a club."
Lennon won five titles as a player with the Glasgow giants before becoming just the fourth boss to lead them to three in a row.
Asked for his reaction to Lennon's departure, Bonner said: "I am shocked. His record is excellent. As a player under Martin O'Neill he had great success and as a coach he was very inexperienced coach but he has proved himself.
"He has won the leagues, that's all he could do, the challenge of course was maybe not there for managers in the past because Rangers have been gone for the league but that wasn't his fault.
"Getting to the group stages of the Champions League and to the last 16 was an enormous achievement for the club because many of us thought it was a step too far.
"So he has done exceptionally well. If you take stock, he is a young manager and he probably wants to try to challenge himself somewhere else."
Former Parkhead idol Henrik Larsson is now the favourite to replace Lennon and Bonner does not think the board will have a hard time selling such an appointment to the club's faithful.
He said: "Henrik is a young manager, he has a huge name as a footballer and had a huge career at Celtic and the fans would live that but whether that would turn into success as a manager, time would tell. Certainly it would be one that the fans would be happy about, I'm sure
"There could be a few names bandied around, the likes of Owen Coyle, Mick McCarthy or even Davie Moyes, who knows about Davie Moyes, he could be one who wants to resurrect his career. I know it is not the competitive league that he has been in before but Celtic is a huge name."