You can find hotel offers for the regionen Graz, Graz Umgebung, Oststeiermark and Thermenland here:
www.graztourismus.at/en
www.steiermark.com/en/accommodations

We recommend:

Best Western Plus Amedia Graz: Website
Contigent reserved until 2018-09-15
Book with password: Rock'n'Roll

IBIS Graz: Webseite
Contigent reserved until 2018-09-17
Book with password: Rock'n'Roll

 a&o Graz Hauptbahnhof: Website