It's done! The cable from Radio Shack came today and after a frustrating hour the project was complete.
I had some trouble running the coax through the speaker/mic. It took a little wiggling of the cable but everything ended up fine inside the case. The real problem was making a hole in the rubber covering at the top of the speaker/mic. First I thought I could make a slice and slip the coax through. Unfortunately that didn't work. I ended up just cutting a hole in the rubber hoping I didn't cut too much and tear the rubber in half. Once I had a hole the right size I carefully put the rubber in place around the edge of the case and the BNC connector and put the speaker/mic back together. I put the screws in and added some rubber cement as a sort of filler for the headphone jack hole at the bottom where the coax comes out and the hole at the top where the BNC connector is.
So far everything works fine. Audio is good and reception is good. To finish it off I need to get a 2m antenna to replace the 2m/440 antenna I have on there now. I have some pics on my site. Take a gander if you want.http://www.enteract.com/~rjs/mic/