In the US McMaster Carr is a good source for stuff like this. Go to
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and put 8732K15 in the search box: 1/2" square nylon bar at $4.10/foot. They advertise that they ship all over the world but I don't know how expensive it will be, so email them and ask. They also have acetal (Delrin) and a couple of other plastics in this size, as well.
-- Regards, Carl Ijames carl dott ijames aat verizon dott net (remove nospm or make the obvious changes before replying)