I have some from different years but they are useless. For modern helmets at least. They complete the look if you want the bike to be stock, and that's what I am after, but otherwise they are way too close to the frame and too tight to be useful for a modern helmet. Having them also interferes with having the grab rails or the grab used for putting the bike on center stand. My model didn't have one, and to fit it I had to remove the stock helmet lock. Which is fine, since I could not use it at all with my helmets. I am keeping them just because they are stock and will go back for the look if and when I wish.
What I do is I take my helmet with me when I park.
1982 Kawasaki KZ1300 A4
1981 Kawasaki KZ1300 A3
assembling engine, chassis & electrical from 79 - 89 parts
Yeah, ideally I'd only get the one on the right hand side (because I have the grab rail on the left), but I won't pass up whichever I can get. Z1300.de used to carry the brackets a couple years ago, but don't any more.
I DO see there's one on eBay as of this posting for 200 bucks, but I don't need one THAT bad.