Tissue holder wall mount.

Hooks into the flaps on the sides of the box, allowing tissue boxes of any depth to be used with the older as long as they're the standard footprint and construction.

Print 2, mirrored. Print with the "outsides" (the side where the hooks are) flat on the print bed. PETG is probably best for the durability and flexibility. Attach to a wall using 3m sticky strips. Mount them while attached to a tissue box to make sure you get the spacing right.

To insert a box, hook in the top hooks into the side flaps and lift. Push the bottom of the box in so it's flat against the wall, and then slide it down so the lower hooks grab the other end of the flaps.

Prusa

I3 MK3S

No

No

Print 2, mirrored. Print with the "outsides" (the side where the hooks are) flat on the print bed. PETG is probably best for the durability and flexibility.