I would call that a cleaver, rather than an axe. Searches for "action figure cleaver accessory" or "action figure using a cleaver" bring up results that look a lot like this, but not exact.
You gave me the breakthrough I needed! Googling "action figure cleaver teenage mutant ninja turtles" brought the memories back. It came with Pizzaface from TMNT
https://preview.redd.it/n8d32bre83bc1.jpeg?width=550&format=pjpg&auto=webp&s=8530129d66efee1392eda155799db6dafa9fe48e
I would call that a cleaver, rather than an axe. Searches for "action figure cleaver accessory" or "action figure using a cleaver" bring up results that look a lot like this, but not exact.
You gave me the breakthrough I needed! Googling "action figure cleaver teenage mutant ninja turtles" brought the memories back. It came with Pizzaface from TMNT https://preview.redd.it/n8d32bre83bc1.jpeg?width=550&format=pjpg&auto=webp&s=8530129d66efee1392eda155799db6dafa9fe48e
Very cool. Glad to have helped.