If the switch isn't available from a spares supplier then the simplest way to source a replacement is to buy another drill from eBay and cannibalise it for parts.
A few years ago I needed a new switch for a 70-year-old planer I was restoring, but no-one I contacted had anything suitable. While searching online I came across a company based in California which stocked the exact switch I required, so I ordered about five of them. A week later the planer was fixed, so I bought another project to work on - a Black and Decker saw of similar vintage, and lo-and-behold it used exactly the same switch... Could have saved two weeks of time and £20 import taxes on a handful of measly parts if I had known better.
Mark
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