Gearboxes are very convenient to integrate with stepper motors, and sounds like the most likely solution by far. Just for completeness, some other options are:
Don't know if this counts, but something fairly common that is a gear, but not a "standard NEMA-xx gearbox", would be a worm gear.
Timing belt with the appropriate reduction. The belts have ...
Actually if you want to keep accuracy and increase the torque you can use a gearbox that reduces the input Rpm.
So you will be Sacrificing the speed for the increased torque and precision.
Its also linear so if you need to go from 200gr to a kg you need a great ratio of. 5.
If you had to go higher than 10 then the forces would be significant and you'd need ...