This guy apparently makes a living from them:
JEEPS - Hood Louvers | RunCool | Hood Vents For Your Vehicle -Hood Louvers | RunCool | Hood Vents For Your Vehicle -
This guy has good prices:
Jeep Panels - Rod Louvers and Sheet Metal design
IIRC, the Pontiac louvers actually had drip trays with them just in case you were worried about the rain ruining your sweet engine detailing....LOL
Run Cools are what my buddy has that have issues with rain causing plugs to missfire after raining. Yes he has replaced the coils twice now with Mopar parts.
Yes the GTP louvers had trays, mines somewhere in a corner, did not allow much airflow with them on and not needed at all