Now, I have been searching and searching for shell or MoP to replace the old inlays. Stewmac doesn't ship overseas, so I spent a week online and phoning around, talking to local luthiers and investigating.
I found out that knife-makers also use shell blanks, and pre-cut MoP for inlaying handles etc. An acquaintance of mine is a knife-maker (Trevor Burger of Burger Knives here in Munster). Oh oh, he just got badly munched on his leg by a shark while spear-fishing ?
I called him, but he was bed-ridden, and had no way to get to his office to give me his contacts ☹
While pondering the situation, I had a close look at the old inlays, and wondered what they would look like if I flipped them around and sanded and polished the back . . ..

I tested on the first one, and it came out very nice, with a bit of a gap around the edges . . . hmmmmmm. . . . brain (?) working overtime here ?
I cleaned them all up (the reverse side, because of the warping, had a nice natural curve to match the radius of the fretboard), epoxied them in place, a little proud of the inlay-slots, to allow for sanding down level with the f/board.
Now, what to fill the gap around the edges of the inlays . . . . ???
Ha, the darkest wood-filler I had was imbuia, so I mixed in some black acrylic paint drop by drop, until I had a pretty close match to the fretboard

Filled all the gaps with the filler, and let it dry overnight. We'll see how this turns out after sanding and levelling ??? I think it's called making a plan 8)