I am selling this item from Amazon: https://www.amazon.com/dp/B0FF22B5LT?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1
It's only been used to demo. With a pull of a string attached to a ring/finger, the blade will deploy and releasing the string tension makes the blade go back. It's pretty cool. 3-D printed. The blade is plastic.
I have several low-priced items that were promotional gifts. See my other listings: Search Craigslist for "Don@95124". I would be happy to combine several items at a larger discount.