Where can I get a part for my old Bosch Classixx tumble dryer?

Hi - sorry - I hope you can help me name the part I need so I can ask for a replacement bit! Took the thing to bits and cleaned it thoroughly. The machine is a Bosch Classixx WTA3003GB/01
The dryer heats, the drum turns but... the hot air is staying in the drum. It appears that the white plastic fan type thing that is meant to turn and draw the air - just isn't. The metal clasp that holds in on the shaft had worked loose. When I refitted it - it all worked for about 20mins. Now its loose again and I have hot, wet washing.
What is the metal clasp/ring called? Do I need to replace the whole white fan thing?
Sorry for using such technical jargon!