First of all a big "thank you" for the makers of this great forum!
I bought "Sagem" headphones , offered at Ebay.
This earphones have a much better sound quality and are also louder than the original parts.
The advantage is, that these headphones have a 2,5mm plug , so that no 3,5mm adapter is required.
I payed 4 Euro incl. shipment only.