Only firm generally trusted to provide this service are Eibach (not sure on spelling) if you use the search facility it will bring you some leads. they mainly do the IS springs but have GS as well. SO I dare Say the LS is on their list...
the good thing about these is they are progresive springs so the ride is not overly compromised.
Welcome to the club and bring your motor along to a meet soon.
Loz