I have never heard of that, but perhaps a Chemist/Pharmacy could assist.
About 30 years ago that's where you could buy it from. As it`s not a fast seller and the plaster goes "Off" most Hobby shops wont sell it. Best place is as Rocks says, Ebay.
Plaster on a bandage, used for modelling
Modroc is the generic name for Plaster of Paris modelling bandage.
This is the same material used in the medical trade use it for setting bones. Perfect for the professional artist and beginners alike - great for kids looking to make some 3D models too. Great for modelling scenery for railways models such as tunnels and landscapes and war games
Easy to use, you simply soak in warm water and shape -