I'm surprised no one has talked about this game yet. But, not that many people bother with a Gamecube...
Anyways, it's a great game despite its deviations from the tried and true Resident Evil formula of gameplay. I had never played any of the Playstation RE's but bought the Gamecube remake of the first one and loved it. 4 very much a totally new and different experience, but I liked the first one and I like this one much better.
The main difference is the camera positioning. It's over your shoulder, full-3D instead of fixed in a room. Probably the next improvement I would say is the collecting of money and the chance to buy more weapons or upgrade current ones. Also the abundance of ammo is great because shooting things is what makes these games fun.
The storyline is very enticing and I'm always promising myself I'll turn the game off at the next save but I usually end up exploring a little more of the next level to see what it's like and end up going all the way. The overall difficulty of the game is very low, since I'm not considered an expert by any means and I've made it pretty far without too many deaths. There have been deaths, but after a few trys it's easy to figure out what you have to do.
I highly recommend this game to anyone with a Gamecube, and even anyone with a PS2 when it comes out later this year.
May I recommend trying Ebay again or possibly Froogle? If these are no help, then I apologize for wasting your time, but good luck in your search.... *edit: eStarland.com doesn't have a copy as of right now.