fmlk,
Looking at the image of Casper Eekhof and seeing the mic he is using, that doesn't look like a Shure SM58 that I used years ago in performance. It looks just like my Beyer M500. Perhaps Shure copied the Beyer look in later years. The Shure SM58 that I used was a fair mic, slender and looked like the Shure SM57 and not too expensive. What it will cost today is another matter.
Derek, if you are looking for just a P.A. mic, I suggest you go to Radio Shack and buy an inexpensive high impedance mic, try it out and if it doesn't suit your needs, take it back and get another one.