gree with garethr, that “Blueprint” parts are probably a more affordable option – a lot cheaper than the £400.00 per unit from dealers and £140.00 on eBay
Blueprint is a name for parts from Automotive Distributors Ltd – their URL to find a local dealer is: www.blueprint-adl.com
GS 300 upper suspension arms (mines a 2001) are:
N/S/F Upper Suspension Arm ADT38693
O/S/F Upper Suspension Arm ADT38692
My local motor factor just quoted me £72.28 incl VAT per unit, so I’m happy. Hope this helps.