I would start here Toll Free: 1-800-234-6151 this is Garrett customer service and if they cant help it will be tough because they have in my opinion the best reps in the business. Anything other than that would be the luck of someone seeing your post here that has old stock at a older service center / new old stock parts. Considering the age of your machine and don't get me wrong here because I would love to have it, you might think of fabricating something that will put this great machine back into service if you are just looking for a handle because they didn't have a rest in the back (http://www.treasurelinx.com/garrett.html) from what I see . For me using a old bicycle handlebar including the grip and using a hammer, drill, vice and some matching paint it would be good to go in about 20 minutes plus time for paint to dry if you are talking about the handle. I understand everyone is not as mechanically inclined as I am but it is pretty simple, find a bar that is close to what you want for the curve (old 10 speed) and flatten one end and drill the mounting holes to attach it to the detector.
