Thanks! This is a great help. Now I just need to figure out my cheapest option!

http://www.usautoparts.net/catalog/?D=kool+vue+mirror+mz13er&Ntt=kool+vue+mirror+mz13er&Dx=mode+matchallpartial&Ntk=Main&Ntx=mode+matchallpartial&N=11207&Nty=1

This seems to be it, but I'm not sure it'll fit a 1999 4 matic. Not too concerned about all of the functionality, just want the mirror to work.