billboard : face X to camera on any Y angle

hi
in line renderer or stretched billboard in particle system if you change the Y rotation, your sprite is rotate around X axis to always be face to the camera
how can i do that?
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look at this images : camera rotation is 30,45,0 (isometric)
look how its a 2D sprite but it look 3D
transform rotation is 0,0,0

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in this image transform rotation is 0,-45,0 (but sprite rotation look like this (30,0,0))

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in this image transform rotation is 0,45,0 (but sprite rotation look like this (90,0,0))

now look at this image its a normal sprite renderer if i rotate sprite at something around 0,-60,0 (if i rotate the sprite in 90,0,0 then you can not see the sprite)

i want this behavior (X face to camera in any Y angle) for my bullets (bullets can fire at any direction but must look 3D from top (isometric view)) and effects in the game
i develop for mobile so i can not use particle system (stretched billboard) or line renderer for my bullets (for performance)
i'm really stuck in this so thanks for any help.