A hum-sized P90 would work great to give you a little more top end, while retaining some of the tone you have now. I love the sound of a P90 in the neck of a mahogany guitar - never mind the inevitable debate about what constitutes a "real p90".
An easier solution would be to solder a capacitor between the neck pickup lead and wherever it hooks on - the pot, the switch, etc.
An easier yet solution would be to lower the neck pickup and raise the polepieces. This gives you more top end, reduces bass, and can be calibrated to still have the same volume as before.
Another solution would be to go to a higher-value pot for your neck pickup's tone control. If it's 500k, swap it out for 1 meg and see how that works for you.
Another solution would be to do nothing, and simply rely on your neck pickup for darker tones and your bridge/middle position for brighter tones. Nothing wrong with this approach either.