You can get them at almost any store that carries electronics....just be sure to find one that doesn't light up in use. LOL.
We had a member in the past that pasted one under the dash of her H's car, it fell out, and he thought it was a bomb. Mass hilarity ensued.....once you get past 51 posts you can read it in Investigative Tips forum.
But, hide it someplace sneaky in a place he would likely talk to OW. The car. Home office. Wherever.
We had a member recently that busted her whole WH's secret life wide open with one, and it saved her from (probably) years of future misery.
It's a good idea. A good place to hide one is in the pocket behind the drivers seat in hubby's vehicle. Too bad you can't hide one in his boxers. Sometimes the hardest part of finally seeing through someone is accepting what you see...
God grant me the serenity to accept the people I cannot change, the courage to
change the one I can, and the wisdom to know it's me.