700C is typically for road, "crosstrainers", and "29ers". Those bikes usually are 32H with 14ga spokes. Cruisers don't typically come with 700C wheels and 700C wheels with coaster brakes are pretty rare.
They do exist, tho:
http://www.amazon.com/Dimension-Coaster-Brake-Wheel-Shimano/dp/B004JKIEFU/
I've never seen a 700C with 12ga and 36H. What you're looking for would likely have to be custom built. Find the hub you want, find a suitable hoop, and get some 12ga spokes, like the Sapims at Holmes Hobbies.
You'd need to figure out the spoke length you need, too. I can't help with that. It may be easier for you to get a custom wheel built at
http://thewheelmaster.com/