G'day Richard,The German Girls is from Coxon's Comic Songster, circa 1858. The tune he gives is Samuel Lover's The Low-Backed Car. I have the dots in Ron Edwards' Big Book of Australian Folk, Rigby, 1976, p 146.
I you can't find a versio of the original tune, I will beat the the dots into MIDI/ABC and post them ... when I get time!
Regards,
Bob Bolton