Do you need a chamber to grow biological material and still retain the ability to look at it under a microscope? Then maybe inspire yourself from this design. It is a simple cuvette and lid that you have to seal at the bottom with a microscopy coverslip.

I have attached the coverslip using a tiny bead of silicon applied with a syringe in the groove located under. I printed it transparent as I needed the plants to grow but you can also print it in opaque colors if you need dark.

You could consider printing it in PETG if you want to sterilize the chamber often with ethanol.