Hmmmm a magnet on the inside leg of a pair of trousers might work. A topit would be tricky as I don't tend to wear a jacket.
Palmed coins usually end up going down my top, but if I'm not careful there I end up growing by a cup size and walk away jangling like a charity box

I can't think of a way to do that with a lapped coin.
Thanks for the idea, abraxus