Print out of a PETG or some other higher temp material. PLA will likely warp in hot agar.
Superglue a short M3 bolt to the divot on the back side to provide a handle.
My file is setup for 0.6mm nozzle, just switch to 0.4mm and transfer settings. It is important for their to be a hollow space inside so it floats on the agar instead of sinking.
The author marked this model as their own original creation.