This maybe of interest to someone with knowledge of electronics, far too complicated for me.
When buying some christmas decorations I came across a cylindrical plastic pack containing led tree lights, very reasonably priced but what intrigued me was a Try Me button on top of the pack which when pressed illuminated the bulbs enclosed. After unpacking the lights I was amazed at the switch which has its own battery power supplied by hearing aid type batteries.
I think the whole pack of lights cost only around a fiver including this little gem. I think they came from B&M discount store if anyone is interested.
If anyone is seriously interested in this I will happily post it to them. Free, how about that.