You should take a look at Yesss!
http://www.yesss.at
1GB costs 20 EUR and is valid for 12 month. ^
I just checked they also do offer a starterkit for EUR 9,99 incl. 512 MB data
Maybe you could also check
www.bob.at. There are more outlets to get the SIM-Card
http://www.bob.at/verkaufsstellen e.g. post office. They offer a starter-kit with 1GB for EUR 14,90.