It's been years since I've seen roof racks for the LS from companies in the U.S. but here is a thread showing that my Yakama Rack fits my 00 LS pretty well even if the mounts are from a Honda CRX I had in the 1980's: http://www.clublexus.com/forums/ls40...roof-rack.html
Would an alternative to be to change how you carry your stuff and reduce how much you take with you? Maybe use soft luggage you can "squish"? I've carried four rolling airline sanctioned maximum size allowed carry-on bags in the trunk of my 00 LS400 with plenty of room to spare.
Roof racks and luggage pods can cause an amazing amount of drag and wind noise - not pleasant on long trips.