The actor is said to have been sending his stylists into the city's back streets for the purpose.
A source told Mid Day: "Imran Khan has taken upon himself to seek perfection and not go with the clichés when it comes to his onscreen persona.
"Therefore he has sent his designers in the areas where he can find the authentic tapori look."
In June, the Delhi Belly star revealed he is planning to meet Mumbai underworld figures in preparation for the role.
Khan has described director Milan Luthria's film as his first action feature, and he plans to "bulk up" for the role.
Watch Imran Khan in the trailer for Delhi Belly below: