I don't use the original "Blu-Tack" and haven't seen it for years, but I remember it well for the 1980's. Now I use a product called "Plasti-Tak" that I get at Hobby Lobby for $1.99 per package. With the exception of being white instead of blue, it looks, feels, and acts just like Blu-Tack did.
If you can't find "Blu-Tack", hope this helps.
[Edit - Blu-Tack was trademarked in Australia, is exported to the U.S., and is available from Artech (among other online sources). Here's a web site]
http://www.artech-electronics.com/us/products/accesso/blutack.html