Mini Anjanath was also my last crown for this quest and I had to farm it like crazy until it dropped.
Best advice I can give you is to do the quest solo, kill the jargas, go to camp and open your map until it spawns. To see it its a small one I found that it helped to place your character next to it and check the size with your character. If the legs are longer then your character, it is not a small one. For my small one the head of my character reached the stomach.
I first killed every Anja but that took too long (because it takes time to spawn it) until I did the size measurement.
If you return from a quest, you get to keep everything and also the crowns, this is the fastest way to farm a single monster in that quest. Capturing or slaying does not matter as I got crowns from both.
Hope this helps and good luck!