I've been searching for a while now. www.diy.com is the website for B&Q and these were made for them by Powerdevil which I suspect is a name for a company owned by B&Q.
I've been in touch and they say they can't find one at the moment but they'll 'keep me in mind'.
I'm not holding my breath.
The switch you need is known as a 'softstart' switch.
That's the result of my searching and I hope it helps. I'm looking for a faulty saw in the hope of getting a switch for it.
Good luck mate !
Raysings
May 2013
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Try fixfault.com to fix drills.