Tha would depend on what country you live in as it has different names in different parts of the world. Sintra is a brand name but what it is at it's most basic is expanded PVC foam. In Australia it has been known to go by the name Palight ® and i'm quite sure in the EU and UK it would have another different name but if you search expanded PVC foam in google in your area you'll find it.
I have built everything from helmet, armour, gauntlets and jet pack using Sintra. Its easy to cut but can be brittle. heating and forming can take time and patience to get the right shape. never over heat!! Once its over heated and it begins to plastically deform your piece will never go back.