This is my Double Action - OTF Fidget Knife. If you want to build one yourself, you can find the 3D print files here:

makerworld.com:
https://makerworld.com/en/models/4492...

thingiverse.com:
https://www.thingiverse.com/thing:660...

printables.com:
https://www.printables.com/model/8634...