Reproduction 240z tail lamps exist on eBay, I'd look at getting those since the "Euro" spec (which seems to be the incorrect but pervasive nomenclature used) ones are very rare to find here now.
You could try via Muscle Car Parts in Sydney.
https://allmusclecarparts.com.au/datsun/datsun-240z-tail-lamp-assembly-pair.html
ebay link: https://www.ebay.com.au/i/273669129478?chn=ps
They look ever so slightly different to the original Koito units, but come with gaskets, loom etc..
If you call them up they might give you a better price than via eBay since they won't have to pay eBay fees. Everyone's a winner, except EvilBay that way.