I searched online for replacements of 50mm and 60 mm and could only find a handful with prices ranging from 400 to 600 INR per pair. Then just by chance I dropped into a local radio and electronic spare shop in Goa, Panjim, one of the old-style shops with shelves lined with resistors and capacitors, etc. They had a box ful of replacement sponge cushions in various sizes. Rs 15/- per pair! I bought four pairs on the spot, to take care of a Sennheiser and a Sony headphones I have.
Try and locate any such shop in Bangalore.