Er yes there is, I got one last night. You just have to grind for it. It will only drop on the last boss as far as I know OR if you're extremely lucky in a chest which you should check for every run. There is only two per run on vet or normal and yes the inferno drops on normal so you can solo it easily but the harvester boss (2nd) is pretty grueling due to the group mechanic that stuns requiring a second person to kill the orbs to free you. However if the orbs hit the boss the stun will be removed so i you solo it always have a long duration HoT up.