I recently purchased a 2000 GS300 that had a section of the piping on the driver's seat bottom missing. The dealer took it an upholstery shop and had it repaired. The piping was not an exact match, but close enough so that unless you knew otherwise you wouldn't realize that it had been replaced. Also, when the car was returned to me I noticed that the lumbar support no longer worked which necessitated a return trip to the dealer for repair. When the upholstery shop repaired the seat, they failed to connect one of the elecrical connectors properly. The dealer found that and fixed the problem. I have noticed that problems with the seat piping are not that unusual on these cars, I'm not sure whether it is faulty material or workmanship.
I'm located in SC, but any reputable ulphostery shop in your local area should be able to repair it for you.