Just an update:
A 6"x10" heatsink set on top of the hood brought temp down to 82F. Not quite as good as the fan, but still decent for being completely passive.
I think I've pretty much made up my mind to go with some sort of LED conversion. Just swapping from a 26watts worth of CFL to 22watts of LED ought to make a little temp reduction. And if the LEDs are too bright, dimming will lower that 22watts which will be even better.