Redknapp was Spurs boss when they qualified for the Champions League with Modric and Bale in the team before both departed for Madrid.
The pair have proven hugely successful in Spain, winning Europe's elite club competition on four occasions.
But Bale, who scored in two Champions League finals for Madrid, has fallen out of favour in recent seasons at Madrid and is now in talks over a move back to Tottenham.
As Spurs thrash out the finer details in that blockbuster transfer, Redknapp urged chairman Daniel Levy to go back to the Santiago Bernabeu for a further shock swoop.
"I'd go and see if I could get Luka Modric back," he told Stats Perform News. "Take the pair of them, Bale and Modric.
"That would be a great coup. Luka is still a fantastic player. That would be amazing.
"I still feel they need somebody there; they've got the forward players, but they need somebody to supply the bullets.
"That's where someone like Luka Modric can play killer passes, into great movement up front. They lack a player like that."
— Tottenham Hotspur (@SpursOfficial) April 26, 2020
While Redknapp remains concerned by Tottenham's midfield, the prospect of seeing Bale join Harry Kane and Son Heung-min in an attacking three excites him.
"That is a scary forward line," he said. "I could see them playing Harry central and Son and Gareth coming off the line and playing.
"I had a silly spell at Tottenham towards the end where I played Gareth on the right and the Tottenham fans were singing, 'He's Gareth Bale and he plays on the left'.
"Well, he's never played on the left since then. He played for Wales through the middle.
"Really him and Son are two players who you'd just want to let go and play and do damage wherever they pop up on the pitch in any of those forward positions.
"It's a bit like at Liverpool, like they do with their front three. They interchange positions fantastically well. And I think they'll do the same at Tottenham."