MATERIAL CHALLENGE: LEGO transparent 2-sided brick with thick non-transparent edges

I was looking for this like 5 days in a row all over the internet and yet no success.

So would any developer or anyone else having good knowledge about creating realistic materials try to imitate this kind of material?

I am attaching some photos of real LEGO transparent plastic bricks: the most significant part - and probably the hardest to reproduce universally for all in just one material - I guess would be those edges where the transparent material should actually become mostly non-transparent and much more darker than the rest of the brick giving us feeling of a full space instead of the UE4 empty gap in between the faces of the 2-sided object (LEGO brick).

Here are some real world examples, take really good notice of that join parts of respective brick parts edges):