Hi tschnoeck,
you can try the stac company (in France), they rebuilt my 4 Ariston shock absorbers (seals, etc ...). Very good job.
STAC (www.suspensions-stac.com)
Porte 12 - 2040 Route de St BERNARD
06220 VALLAURIS FRANCE
Tel: 0493646001
mail: info@stacfrance.com