Good news, I had an exact replacement for the upper balance hole jewel, I was about to call in a priest to exorcise the curse 👿
I have a good selection of ruby jewels and although the original was not the ruby type, the new one is and will provide a warm, rich, red glow through the lesser garnet cap 
I was also able to rub this one back in to the setting so better than new, I believe the jewels made from rubies provide a better bearing surface, although I may be delusional in my reasoning 🙄
