I had the factory bags replaced at Earnhardt Lexus
6905 E McDowell Rd, Scottsdale, AZ 85257
If you think that it's possible the bags are fine but something else is going on, a Lexus dealership is about the only game in town that is going to be able to properly diagnose what the problem is.
The dealership though definitely the most expensive option.
If you decide to convert to a steel coil kit, I unfortunately don't have a good place to recommend, most of the suspension work I do myself, but I would think almost any shop could easily handle the job if you brought them a kit.
I don't have any first hand experience, but there is such a kit from Strutmasters
I would figure $200-$300 in labor to install, so you're in the $600- $700 range after everything.