CSR Bradford makes lots of Glasswool and Rockwool insulation products. Glasswools:
Multitel, Flexitel, Supertel, Ultratel.
18kg/m3, 24, 32, 48.
1.1pcf, 1.5, 2, 3 pounds per cubic foot.
Bradford don't sell direct but possible sources include Gyprock Plaster Lining Centres (I think these may have been re-branded) and possibly air-conditioning ductwork suppliers. You could just ring Bradford 02-9765-7100 and ask where the public can buy the stuff. The web site includes "where to buy" info but this is mainly for home thermal insulation - still could ring and ask your nearest listed supplier about the denser stuff.
"Duct board" is an ACI brand name (I think ACI is now called Insulation Solutions) and is approximately equivalent to Bradford's Quietel product, 130kg/m3 (8.1pcf). Costs a motsa!
There's some good info on
www.bradfordinsulation.com.au including a Design Guide with absorption test data for many of the products.
edit: materials are available as "board" and "blanket" except Multitel (roll only). Board is more rigid (2400x1200), blanket is a roll up to 18m long depending on thickness. List price for 50mm plain unfaced Supertel should be around $22/m2. Black matt finish (BMF) adds about $7/m2.