Where to buy Polystyrene filling for bean bag sofa?

Where can I buy Polystyrene filling for bean bag sofa and pillow?

The corner shop selling sewing materials located within Park Hotel.

Does anyone know the price of say 1 kg? Don’t know how they sell it, might be in litres? I’m not in Miri most of the time, so can’t check myself. Would appreciate any relevant input from you guys. (Y)