Took the original model and used OpenSCAD to add three 3 mm holes to the bottom of each object.
Cut three pieces of 3 mm filament to just less than 2 cm.
Insert all the way into the three holes in one half of the model.
Apply glue to the surface (enough but not too much) and line the filament up with the holes in the other half and push together.
Clamp and allow to dry.