Do try the hardware shops at Kelantan Lane. If you're looking to soundproof your room, then it's best to source out the appropriate materials. Assorted materials of varying density and shape do a different job in acoustic isolation.
For smaller amounts, I can recommend getting from UVnium in SLS B1, Digimall. Look for Gary there and ask him for the pricing. He does keep some stock for noise isolation jobs on computer casings.