I am looking for a manufacturer(s) of cartop carriers (the hard
plastic kind). I don't need retailer/distributor information for
existing companies like Thule; rather I want to contact original equipment
manufacturers. Can you provide an answer to my Google question? Thank
you.

Thule, Thule, Thule.  In the hard shell category, I'd say there's
certainly room for competition, because in a brief search I found only
"softie" competitors.

The closest was the hard shell end but soft middle bullet design:

http://www.piggypack.com/website/cartop_carriers/cartop_carriers_intro.html

I couldn't find anything conclusive. Here is what I got :

Car Racks Direct
http://www.outdoorsports.com/osc/crd/products.asp?dept_id=15

Rooftop & Cartop Cargo Carriers Index (soft/hard carriers mixed
listing)
http://www.roof-top-car-top-cargo-carriers.com/ind.html

Sports Rack Vehicle Outfitters
http://www.sportsrack.com/

YAKIMA  PRODUCTS  CAR RACKS  CARGO
http://www.yakima.com/products/cargo/index.html



Google Search Terms :

hard OR shell cartop OR car-top OR "car top" carrier OR carriers
manufacturer OR manufacturers OR maker OR makers OR roof luggage
carrier
://www.google.com/search?q=hard+OR+shell+cartop+OR+car-top+OR+%22car+top%22+carrier+OR+carriers+manufacturer+OR+manufacturers+OR+maker+OR+makers+OR+roof+luggage+carrier&hl=en&lr=&ie=UTF-8&oe=UTF-8

hard OR shell cartop OR car-top OR "car top" carrier roof luggage
cargo
://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=hard+OR+shell+cartop+OR+car-top+OR+%22car+top%22+carrier+roof+luggage+cargo+