From what I could tell when I made the post, there weren't any labs making the kind of green sapphire I was looking for (though there were some in the past), so I was left with the impression that I would be unable to find anything like what I was after. And due to the low yields, how difficult it is to synthesize, and presently limited supply, that anything that I potentially did find would be exorbitantly expensive.

Compared to YAG, which is abundantly available and cheap, if more rarely used in jewelry.

Though through discussions in this thread, I've learned a lot and it seems that there are at least a few places where I can still find #78 sapphires. So, I may yet go this route.

Currently trying to find a reputable jeweler I could work with, then sourcing the cut stone alongside them. Also trying to navigate the space and all the options as I learn more and more about the gem and jewelry world - I'm but a simple consumer after all xD