There are a bunch of keyholders here, but most of them are swiss army-style and quite bulky. I tried to design my own. It holds 5-6 keys.
And I tried to do a "tactical" style, because why not :)

You just need a 20mm m3 screw and nut.

there are also optional 0.5mm shims to compensate for gaps and an optional axle sleeve to prevent slack.

Creality

Ender 3 Pro

No

No

0.2

25%

I recommend 3 shells and you'll probably need a brim to prevent warping.