It's not just the mounting holes. You need to duplicate impedence and power handling capability also.

I found replacements for my door tweeters by finding people who were parting out wrecked cars. This is a great source, someone will see your post and reply. Also, you can check eBay and there are many parts houses out there that can get you oem parts. There are a couple of guys here who have done complete refurb on their systems, you might look to them for ideas. Also search the archives.