Try to get in touch with the Chamber of Commerce, and get a list of motels/hotels in the area. A lot of the little places don't advertise, and get overlooked for a while.
Also don't forget about bed and breakfast type places. They are a little more expensive, but much more quaint and homey, and they usually have killer meals included in the price.
When there are big events like this, some people will rent out rooms in their homes, so maybe you can get some info on that too. Check with family, friends, cc-com forum members, etc. Maybe one of them would be willing to put you up for a few days, or know someone that will. They do that around here in all the time during hunting season. Hey, any port in a storm.
Try expanding your search farther away. Everyone tries to get as close as they can, but you'd be surprised how many rooms you can find 60-90 minutes away. It's better than not going at all, and you're only going to make the drive twice a day, so its not that bad. Heck, I used to drive an hour and a half each way to work every day.
If you don't mind roughing it, you can check for campgrounds in the area. You may have to sleep in a tent, but they have showers and other amenities, so its really not that bad. If you have a truck, see if you can rent a camper in your area, and use that at a campground. Motor homes can also be rented, although they'll kill you in gas costs nowadays. Maybe you could find a rental place close to the event and pick one up there.
As a last resort, go there the day before, find a good parking place, and just sleep in your vehicle. One time, I took the family to Georgia for a week. Going down, we had no problem getting a room, so I didn't worry about rooms on the way home. Unfortunately, there was some type of national Fiddlers Convention going on, as well as Corvettes at Carlisle. There were no rooms for hundreds of miles, and I had been driving for like ten hours straight, so we just pulled into a Holiday Inn parking lot, and slept there, in the car. Wasn't the greatest experience, but not the worst either.
Either way, good luck on your adventure.