Living in China, I couldn't find a supplier for a "Fork Cork", so I whipped up this design for the underside of my Rockshox Pike steerer tube. Works nicely so far!

Printed the top and bottom in PETG for some durability & weather resistance.
Printed the middle/wedge part in a flexible TPU.
Designed for an M6 bolt & 10mm nut.

Not sure about the durability... If the wedge is soft enough, you shouldn't need to over-tighten the bolt to get a secure fit. Over-tightening will definitely crack the caps!
Plan is to put lightweight supplies inside & forget about it (cash, patch kit/tire boot, quick-link, nitrile gloves, etc)

Creality

CR10S PRO

No

Doesn't Matter

0.2

30% caps & 10% wedge

I printed the caps with 4 perimeters & 30% infill for some strength (might want a bit more)

The wedge was printed with 1 perimeter & 10% infill (hexagonal) for squishy bendy properties.