There are at least two possible solutions:
1. Use a tractor, or steering wheel, knob, as in the first picture. The knob in the picture came from ebay and these are not for sewing machines, but typically on a tractor to allow the wheel to be turned with one hand. The advantage for this application is price, about $13 for the one I bought and ease of installation (there is some cut up rubber inner tube from a bike tire under the clamps); the disadvantage is the turn ratio is 1:1, meaning one revolution of the knob gives you one cycle of the machine, i.e. one stitch, whereas the typical after market hand crank is about 3:1. This 1:1 ratio makes for some tedious sewing if there's any volume involved.
2. Add an aftermarket hand crank. This option, at least for me, is only theoretical as I started it on a machine but never finished, so take it with a grain of salt. You would have to tap a hole under the hand wheel into the pillar in the correct place to allow a crank to line up with the hand wheel, two holes actually, one large and one small. The small hole would be for a smaller bolt and would keep the crank in an upright position. You can see in the picture the shiny bolt on the right of the pillar; that machine is also a treadle only 27. You would also have to drill an extra hole into the hand crank itself for the small bolt, and shim out the hand crank with washers to keep it as vertical as possible in relation to the hand wheel. Plus, I'm not sure the typical after market hand crank will spin a 6 spoke hand wheel, which your machine likely has, which means it may have to be replaced with a 9 spoke hand wheel (if one will fit onto the shaft of an older machine). You can see why I never finished this project.