Make them yourself. I'm finishing my custom belly pan now, and then the brake ducts are next. I've already test run 2-1/2 duct and that's about the biggest you'll be able to run through the engine compartment and right up to the hub. I just bought spare dust shields at $5 ea and using 2-1/2" coupling for exhaust system at $3 each. This will be cut and welded to the dust shield to attach the hose.
For the intake, I'm using a brake duct headlight mount. I'll need 3" to 2-1/2 adapter since I have not found mounts with 2-1/2" fittings. This will be mounted to the left and right of the lower grille area. There's a plastic air damn that can be cut and the headlight mount attached.
Here's a picture of how the dust shield would like (not from a Camaro). Once I finalize how I'm doing this, I'll post the pics.