well we would need to know the make and model of your 1k W circular saw. SO need to provide bit more info.
No need at all to know the make and model of ya Saw, just the full load rating that's all. Check out RS Components for Foot Switches.
can i ask why a foot pedal ?? with a circular saw you need both feet firmly on the ground or moving in a comfortable safe manner with the saw stopping if you loose your grip if its under a table then you should be using a nvr[no volt relay ]that you can reach with your knee or hand