It'd help if you told us where you are.
For example; I live in Tallahassee Florida USA, I have 3 choices:
1) Shipping from any variety of places.
2) Drive 2 hours east to Jacksonville SPI for cash and carry
3) Drive 5 hours south to Tampa SPI for cash and carry
We have family near Tampa so I sometimes try to grab a few blocks of rock wool when it is convenient to stop at the vendor on our drive home. (I have a mini van)
It is most often used in ships, factories, and hi-rise buildings for the combined features of noise and temperature insulation. You can often find suppliers that serve those markets will carry a suitable product.
best regards,
mike