The elusive G109A maintenance manual was found (special thanks to Gerald Suhrcke in Bayer who had a copy). It is attached here (German only but we are just glad to find it) along with the G109B maintenance manual in English just in case anyone does not have it as well (plus other related docs are in the link below). Thanks Gerald!!
https://drive.google.com/drive/folders/1sPaPYyR_YJ-EAo3iTY8-Tcr5vz0J9Bux?usp=sharing
Grob-G109A-Maintenance-manual-Rev7.pdf
Grob-G109B-Maintenance-manual.pdf