The starter is from China, of coarse, and for a motor scooter. I tried one from a Yamaha Jog that was a little smaller and did not have quite enough strength.
There is really no magic to this starter business. I've used toothed belts, gears and chain to drive the crank. All work but the geared ones can be noisy. These little starter motors draw a lot of current so I like to use a scooter solenoid. Have tried big 20 amp starter buttons but prefer the solenoid route.
If one wants to make a starter I suggest getting the parts together and figuring how to make it work. The main part is the one way bearing, aka a sprang clutch, roller clutch,etc. On the Hoglet I used a shaft lock device to clamp on the crankshaft the outside of the shaft lock locks onto the 3/4 bushing the roller clutch rides on, the outside of the roller clutch is a press fit in the chain sprocket.. Every one of the four electric starters I've done are different in many respects but it's really straight forward.
I made changes to Randall's published design. Bigger crank discs, 4 1/2" vs 4". Different valve train allowing for hemispherical heads and 1/2" valves vs 3/8". Also I made two cams shafts which allowed more options re valve timing, duration, lift. In his original article Randall discussed opening the exhaust valve early to make the engine "bark". I decided to try this because most Harleys are loud. In fact, listening to one idle with a loud exhaust note, even at idle, I'm convinced that's what Harley has done to make their bikes extra loud. So I am opening the exhaust real early, while this must sacrifice some power it's only a model.