Will the common 28BYJ-48 fit the bill? Maybe use a 'coupler' to go from 5mm slotted shaft to 7mm shaft.
Inexpensive and readily available on Amazon with and without ULN2003 driver board. I don't know what their N-cm rating is.
https://www.amazon.com/s?k=28byj-48&crid=2LJRSFDK38ZLB&sprefix=28byj-48%2Caps%2C74&ref=nb_sb_noss_1
Datasheet
- Pull in torque: 300 gf.cm
Hmm, so maybe a little low.
These geared motors will do 70 oz-in = 50 N-cm