carbalite ores are very, very, VERY common. i have over 300, but it is a high rank ore. You can get it on the two highest mining points in the farm or once you are HR 4 you can do high rank gathering to get them.
As far as "just thunder sacs" go, you need to kill a high rank Khezu (HR 4 and up)
Trust me, i didnt get True devil slicer till i was HR 5 doing "Land of Tremors too get to HR 6.
I wouldnt count on getting it soon lol