This is a puzzle that i design, is based in the self geometry of the puzzle itself. You have to join the core with a M3 by 8mm. You slide the other pieces in being careful to place them in the right order, so it forms a disc. You can close the top with a little bit of glue.

Edit: If the center with the 4 coupling rods does not work try the 3 version one and if it does not stay in pllace use some ca glue for securing the caps.