I browsed the birth index a little - 'Sontag' is there as mother's maiden name, but also misspelled on some other records I think. A couple of other thoughts - check your area libraries to see if they have Ancestry Library Edition available for use in the library. I haven't tried it (yet) to see what the differences are vs the individual subscription but it could be helpful. Also the MN Genealogical Society http://mngs.org/ has a statewide cemetery project under Resources - it looks like Morrison County Historical Society may have some cemetery transcriptions.
Good Hunting!