Precision Matthews has one for $300. That seems to be the best option. MSC, Travers, Shars (on Ebay) and Align have some as well. There's lots of cheaper ones from sellers like Vevor, AliExpress, and Temu, but I'm staying away from those. I need to check the torque specs as well; they all LOOK the same, but a careful reading of specs says they have different torque ratings.
I still might make one, since it seems like a good project to practice my skills on. I can show it to my college students, too. I only needed 10 kg-cm of force under a load to turn the handle so I'm not sure why these motors all need so much torque. I could compromise on speed and that would allow for more torque.