There are some decent 3rd party keyboards that are made for OS X, and they will have most of the hardware control keys (brightness, volume, etc). Google it, and I'm sure you'll see some good stuff.
Personally, I just found the old Apple keyboard to be better overall. It's simple, clean looking, and was only $30 (USB/old design). If you can find one of the old ones (shouldn't be too hard if you check local electronic retailers who are clearing out old stock), that might be worth it.