I was actually looking to source some on/off/on toggle switches - how exciting. Not.

But searching on eBay found me (copy and pasted)-

K-II KII K2 EMF meter / NEW Customized w. On/Off switch

TAPS GHOST HUNTERS w.battery & paranormal instructions!

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THE HOTTEST PARANORMAL TOOL ON THE MARKET!

Brand new K2 meter re-built with a constant On/Off switch* for your convenience.

GHOST DETECTOR & SPIRIT COMMUNICATION TOOL! IT TRULY DOES WORK! Read our Testimonials at bottom of page!

Preferred by psychic/paranormal researcher Chris Fleming from Biography Channel's "Dead Famous" !
Preferred by the ghosts as well! Seriously!!!!! This meter gets readings that other meters don't pick up!
Easy to carry with you in your pocket or purse! Fits in your hand and weighs only 3.5 oz!

And it can be all yours for under $80. Bargin!