Number

upper and lowercase letters

symbols

All those characters should be easily accessible. Maybe divided in 3 sections, with randomizing mechanics. (generating random patterns requires effort)

- when you press a key, it blocks itself and a common other key, until you press a totally different key.

- or that a key pushes other keys away, changing their position and likely hood of being pressed.

getting those characters at paper is another thing, but what is most important is storing them somehow. Later on you can easily write it down.

- use metal characters that you can collect into a bar and connect the keys in a random way to those metal characters

- print key presses directly on paper but make the paper move to the good place.

- maybe some other way too.

use some drum sticks and smash your password.