Reddit mentions of (Red)Simulation Light Up Thumb Tip Magic Trick Fingers by M-zone Co., LTD

It’s quite simple but very effective.

It’s a toy thumb that is the same colour as his skin and it has a little switch inside and when you push down a light comes on.

https://www.amazon.co.uk/Magic-Street-Magician-Vanish-illusion/dp/B0184TERTI

I remember when I first saw them in Harris’s. I was amazed as a child.

My grandad used to do this with me every time I visited him. I loved it so much but always kept his secret safe

I found out a few years later that he wore a thumb like this: https://www.amazon.co.uk/Magic-Street-Magician-Vanish-illusion/dp/B0184TERTI