You could drill the hole(s) for the switch using a bit of the proper dia. Then, use a rasp and sandpaper to clean up the edges.
OR, drill smaller holes at each corner and use a scroll saw to cut them out.
All mine are paddle switches or I'd measure one to find the closest bit diameter.
'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton
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