Ecat24

[James McGrath]

This website can come in handy for looking up part numbers.

http://ecat24.com/opel/catalog/models/1/

If you are worried about what parts fit your vehicle, just enter your VIN number and it will narrow the search for you.

[James McGrath]

Ecat seems to be experiencing technical difficulties at the moment.
Fingers crossed it will eventually be fixed but in the meantime, here's an excellent substitute:

http://www.catcar.info/en/