Alternate source of creature mastery sigils

Is there another way to get creature master sigils, and if not, can there be one added? I can appreciate that they should be difficult to get, but after 150+ realm depth farming Land of Breath and Balance and getting 7 beacon mastery without a single sigil (accidentally wasted the first one, unsocketed the wrong artifact), this moves from “difficult” to “frustrating”. Did get 4 storm sigils though. >.>

Anyways, somewhere to buy them once your creature mastery is high enough would help a lot, perhaps the arena at rank 30 and the respective creature mastery at 10? or something similarly “you did the footwork, here’s the reward” kinda investment. The randomness is the issue I’m having, not the fact it’s a difficult task.

I can get the trait material for prettymuch any creature that has one through assassination missions, so mastery sigils being a little more reliable in some way would help a lot with planning builds. Especially with my tendency to mess up artifacts.