See also:
Inflatable kayak glues and repairs
Repairing a Gumotex Seawave
MYO alternative to D-rings
You can get Chinese PVC D-rings dirt cheap on eBay but genuine hypalon D-rings (not PVC claiming to work on hypalon) cost a lot for what they are. Once you factor in the price of two-part glue, it adds up, especially if you have a few to fit.
It’s fairly easy to make your own D-rings for your IK to attach gear, thigh straps, footrest mounts and so on.
Heavy duty Grabner D-rings. €15 a shot 
Half a square foot off-cut: £9
You can buy metal D-rings by the sack-load online, as well as round PVC or Hypalon patches. (‘Hypalon’ is pretty much the same synthetic rubber as Gumotex Nitrilon and Grabner Nordel). Or buy an off-cut (above right) for much less and cut your own. A D-ring doesn’t have to be round but it’s better if corners are rounded. You will notice how unusually hard it is to cut this stuff with scissors or a blade. The fibre core is tough: good for zero-elasticity in an IK.
Pictures below show how to make your own D-rings.
Go to this page for how to apply any patch, step-by-step.
A small but thin 75mm round hypalon patch for light duty use. Cut a slot in the middle wide enough for the D-ring.
Trim the smaller round back-patch to fit the D-ring. Rounded corners are best.
How it looks from the back.
Ready for gluing.
Glue drying on a batch on D-rings along with the two Grabner D-rings. On my single-side coated patches I glued coated green topside to uncoated grey underside of the round patch. When the glue is dry, carefully pass the D-ring through the slot then press down hard on the two surface with a tyre roller or in a vice.
Finished D-rings recycling some old Semperit metal Ds. Not sure I’ll be opening a D-ring shop, but they will do the job. See here for how to stick on.
Sticking to the Rules
I needed to fit some tube-top D-rings to properly support a second backrest in my Sunny 2020. I found a stray, opened tin of Bostik 2402 two-part in my kit bag, but with an expiry date of 2009. Back then I only owned this original Sunny and looking it up, 2402 turned out to be for rubber boats. Perhaps I bought it more recently but didn’t notice the expiry date. In the tin the glue was still liquid and unseparated, but the little bottle of Bostik D-10 hardener had long since evaporated. Digging around, I also found an opened bottle of PolyMarine hardener. Comparing chemicals showed they both contained Diphenylmethanediisocyanate, one of the few words that’s too long for a Scrabble board.
I mixed the wrong-brand hardener with the 11-year old glue 25: 1 and the bond looked as good as anything.
Drying… drying… 
Done
