tar heel guy

Unfortunately you'd have a really difficult time finding replacement air struts for your LS. 

For what it's worth some of the coil conversions ride pretty great and end the hassle you're going through.

I hope the '13 has a better air suspension than my '09 :(

This looks like a known issue with your car. Here's a .pdf from Lexus that may be useful to you! Hope you can get this sorted!

http://www.revbase.com/BBBMotor/TSb/DownloadPdf?id=173799

Great info! Happy to see the aftermarkets are working for you.

sorry to hear you're getting raked by your mechanic. 

it's not a very complicated job to replace the control arms so pretty much anyone with a set of tools and access to a lift can do it. just buy the parts yourself (make sure to double-check everything) and find someone local who is willing to give you a reasonable labor quote.