Switch to a 4231 and sign James Rodriguez. In the CAM role he can make up for Pogbas output.
If we are sticking to a 433 and want a Pogba replacement in CM then its impossible. No other midfielder can hold players off, dribble, pass, cross and have the vision Pogba has. Savic is a tank who can hold players off but his passing isn't as good. Ndombele has good passing but he doesn't have Pogbas frame.
The best Pogba replacement would be to replace him with two efficient CMs who may not possess his attributes but are consistent in their output. We would also need a winger who can add an extra 15-20 goals and creativity across the front three. If we replace Pogba with CMs who can occasionally chip in but focus on getting the ball to forward players then they will also score more and we will be a better unit. It should not be underestimated how reliant we are on Pogba to create, without him we are shockingly average going forward.