Here is my homebrew variant of the true strike cantrip:
Components: V, S
Casting Time: 1 bonus action
Duration: Until the end of the current turn
When you roll a 19 on a weapon attack, that attack is also a critical hit, then this spell ends.
This spell is brewed for my players' Arcane Trickster, who would like a combat cantrip that will enhance his Sneak Attack. He does not like true strike because it wastes one full turn before he can attack, so I made this one require a bonus action instead.
I'm worried that making it require a bonus action instead of an action will make this overpowered.
Is this homebrew spell overpowered as a cantrip? If yes, what is the suggested spell level for this? What can be modified so this can stay as a cantrip?