Do you have a decent hobby shop in your vicinity? If so, it should be able to sell you some brass wire of the appropriate diameter.
I'm not quite sure why Heller came up with the idea of using wire for that purpose. The real portlid tackles, of course, are rope. They're secured to ringbolts in the portlids.
Several other features of that kit don't make much sense in terms of materials. If Heller was willing to include wire in the kit, why not use it for the hammock netting stanchions? The plastic ones are just about worthless, and making them out of wire would take a few minutes.
It looks to me like the designers got so fascinated with making clever jigs and gadgets (their solution to the Great Ratline Problem strikes me as the most ingenious, and most ridiculous, yet) to the point where they couldn't see the forest for the trees. To provide a jig for making hammock nettings (far better - and simpler - represented by nylon mesh from a fabric store) and simultaneously forget to provide any means of fastening the yards to the masts....In many ways it's a magnificent kit, but in others it's downright irrational.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.