B&W is excellent about keeping Replacement Drivers for Legacy Models. I would not mess about with a substitute Driver when the one specified was designed specifically for that CC. B&W makes their own Drivers which only a few other Speaker Companies can also claim. Subsequently, they are able to custom design each Driver for a specific application. It would be a huge mistake to put in anything but the correct B&W Driver.
You can search the site in several different ways, provided you are able to find this site. I don't remember exactly how I found the B&W Parts and Price list but I remember making several calls.
This is the way I prefer to use the Parts listing http://bwgroup-support.com/partslist.html I believe the driver you are looking for is priced at $228. B&W parts lists are well maintained you can take a price listed to the bank.
If you delete everything to the right of the forward slash in the address line you will end up on the main support page (of course). You can search for your part in several ways. I prefer the parts list because I like to think about upgrading drivers and crossover. I haven't done this yet because $2600 for the diamond tweeter is a little pricey.