1) As the LNF is not a common engine outside of North America, there is probably not an after market water pump available. But, Google may be the best method to research that. As it is, at ~$1.40 to the Euro, that price may be reasonable once shipping, import duties, and any other taxes are added in.
2) Can you clarify the year and model of you car? There were Solstice GXPs built in calender year 2006, but they are all 2007. The only 2006 Solstices were all 2.4 non-turbo power cars. There are no 2006 GXPs (unless your country goes by product date versus manufactures model year designations).