> Could anybody give me some pointers / directions, please?

Epoxy resin. You can buy small quantities off the shelf in hardware
stores in 5 minute or 24 hour versions for D-I-Y. Avaliable as clear
or cloudy. Or as a potting or encapsulation compound from electrical/
electronic suppliers in black form. It will take some serious efforts to
find out what's been encapsulated

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