Have you done the push test...you push down on one at a time and see how the spring back from the shock does. Not knowing how many miles and the condition of the roads, but shocks can last up to 150K miles. If you are looking for OEM replacement call SunCoast in Sarasota, FL. They have really good prices for Porsche parts. You can also check with Pelican and see what they carry for replacements.
PelicanParts.com - Porsche Boxster (1997-04) - Suspension
Boxster (986) 1997-2004.5: Porsche Parts & Porsche Accessories - Wholesale Porsche Parts & Tequipment - Cayman Panamera Cayenn