manufacturers

Hey guys. Newbie here. Got a serious itch to buy/build the mini bike I never had as a kid. Not sure the best route to go but I think building one would be pretty cool. I'm wondering who currently manufactures mini bikes new? Only one I've found is Taco and they sell kits so I'm leaning...

I just got this frame from my cousin. The only thing i can use to identify it is a number etched into the handlebars, on the plate where it attaches to the frame. The number is B3868-39. Couldn't find anything on Google. It looks most like a Bonanza, but so many manufacturers at the time made...