where you have the 32nd note figure
split it with one hand
Fingering 1-3-5-1-3-5-1-5.
I agree. @ R_4 - I'm a little surprised you haven't encountered this particular thing before.
My edition (Schirmer) makes it really difficult to understand those as 32nd notes, so that explains my confusion. Should be ok to play it with the right hand. Doesn't matter in some ways, frankly you have bigger issues to worry about in general with the concerto.
If you split it, you've got your hands moving in opposite directions - RH up to that C# and LH down to the bass. Twice the risk, and less coordination.
If you're unsecure about the top c-sharp note, then use 3,4&5th finger at once to hit that note.That works pretty well!