Skidmarx makes them in England- closer to Portugal than Sharkskinz, who make them in the USA. There is another company, Catalyst Composites, that make them in the USA as well.
Catalyst Composites
Sharkskinz
Skidmarx
There may be some others, too, but there are three that I know for sure. I have a set of Skidmarx plastic to put on for trackdays, and I am happy with it.
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