For the front, I haven't found any suitable replacement center bushings.
For the rear I use Energy Suspension busings. The LX rear sway bar is a 5/8" diameter, and that size should be available to most any parts shop who carries E.S. You'll need to trim the U-Bracket that comes with the new bushings in order to make it fit OEM-style on our rear sub-frame. When you take it all apart you'll see what I mean.
If you find the bushings and need some help with the installation, hit me up via Email or IM and I'll try to better explain what I did to install those bushings.
It does make a difference. :tup:
If you make the switch to a GT rear sway bar you'll have to switch to 3/4" rear bushings. The GT rear bar is (as you already guessed) a larger diameter. It's noticeable when you change over. ;-)