Probably — I get the impression that the set only includes the etched parts. 1 mm plastic rod is easy enough to get, though: Evergreen sells bags of it, as do other manufacturers. 1 mm copper wire is easy enough too, at least outside the USA, where I suppose you may have to look for whatever the equivalent American copper wire gauge is.

When I look at the instructions, BTW, that set looks like a lot of work. Folding the lower edges of the seats will be tricky because it's such a small lip you have to fold over, and cutting tons of seat supports all to the same size is also not that easy (or fun) a job.