Take the seat to your local upholstery shop and they can recover it or repair the foam. You can also get Travelcade seat covers from DennisKirk.com. Pipes are available from Kerker, etc. still but are very expensive. For a fairing check Airtech.com.
Some model differences, but nothing too major. 85 (A2)and 86 (A3) US
In Europe, Japan, UK etc the bike is known as the Gpz900r and had run from 1984 - 1996 (A1-A8)
The main difference would be in the later years they went to a non anti dive unit and 17" rims instead our 16" rim in the front and 18" in the back.
Parts are available through Kawasaki and when not available or not a cost effective soloution through salvage yards and of course, don't forget ebay!
With the bike getting older I have considered getting a whole parts bike to keep it running right. Initial investment is more, but cheaper than going to the dealer all the time!
For the seat just go to a local fabric store (jo-ann fabrics here) and buy some new vinyl.
they usally have a bunch of colors and styles, here they have about 10 differenct types of vinyl, I bought some plain black.
You can then stretch it around the seat and use a high power staple gun to staple it underneath, I used a staple gun that runs off of an air compressor.
I have an 86 gpz900 and most of my parts have either come from ebay or bikebandit.com. They or a site like them should have pretty much any OEM parts you need but they won't be nearly as cheap as other options.
I think concours and eliminator are rather similar and should have interchangeable parts that might even work as an upgrade.
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