That's looks like a bonanza and you might be able to use a drum brake with that sprocket or you are going to have to fab up a custom brake (hydraulic is best). Scrub brakes are not bad at stopping but are hard on rear tires
Can't tell if the scrub brake is a later add-on or not. But, I like a rear brake operated with the right foot and a front from the right grip....just like a motorcycle so it's a technique that translates across both platforms.
Is one brake adequate for a mini bike? I don't know.
Good advice. I've ordered from MFG before. Nice big order too since I wasn't worried about an escalating shipping and handling fee--just a flat rate with them.