Where can i get a flame totem gem?

[Losse]

Im a level 20 scion. People tell me to buy it from nessa but she doesnt have it.

[Psyringe]

Scions don't get the option to buy that gem from Nessa.

Create a Templar and quickly play it through the "Breaking some eggs" quest (where you collect the glyphs from the Rhoa nests, and use them to open a secret passage). Afterwards, select Flame Totem as a reward from Nessa, put the gem into your stash, and retrieve it with your Scion.

Alternatively, use a marauder or witch, and buy the gem from Nessa after solving the quest. The new expansion has made it much easier to get specific gems, since they can be bought from vendors now, but each class gets its own selection of purchasable gems.