There is a full list of regulations provided for the MLRC Rallycross at http://www.mlrc.ca/rallycross/regulations/2011/Rallycross%20Rules%20-%20Master%2...

But for a quick summary, for the rallycross, you need a road worthy car(ie, won't fall apart on the track) and a helmet which meets the required safety regulations(Helmets bearing "Snell Memorial Foundation" 1995 M or SA (or more recent)). I'd suggest bringing a spare set of tires, and investing in a skid plate. Those aren't requirements, just recommendations.

Someone else will have to fill you in for the navigational rallies, but the two that I participated in, you just need your car, and a codriver with a pencil, calculator and some gravol

I'm going to go out on a limb and say picking up a used one for a 1994 Honda accord will be impossible  

Best suggestion would be if you know any fabricators...essentially, they just have to cut a large piece of aluminum into shape, and then drill holes to match up with the existing whole where the factory skid plate would exist.

Again, this is not a requirement, just a suggestion. If you drive safely, you shouldn't have any issues racing without one, so if you can't get one, its not the end of the world. I ran my first few races before getting one, before I was sure that racing in all the events was something that I wanted to do.

My best suggestion would be to grab a measuring tape and get under the car. Throw your measurements on a piece of cardboard, and then get back under the car and make sure everything lines up.

Where are you located? There's a guy named Tom who comes out to the rally-x events and owns a metal company. Hes located in Peterborough, but I'm sure he'd love to help out.

The skid plates don't have to cover everything, just under the engine, like your factory one would.