Might I suggest mounting it low, using your left rear rack strut eyelet. Looking at a photo of the CherryBomb it looks as
if it uses a clip to attach it to the seat post clamp. Perhaps with a little judicious cutting/ trimming of the clip assembly
and with a single short seat stay rack strut bent and trimmed to the proper length, you could fashion a short support
to hold the CherryBomb secure.

I know... you're probably looking for a simpler solution; it's just the wanna be fabricator/ mad hatter designer in me.

I can kind of see the design in my head, though...

Alan