we ended up getting one.
The 3 major vendors I've come across are Massimo (the one at Tractor Supply), Coolster, and X-PRO.
I believe they all have the same Chinese 125cc engine, which may be a Honda clone.
As far as I can tell, they all have IFS and a chain driven solid rear axle which is set up to move like a swingarm (since you wouldn't want the rear sprocket to twist out of plane in articulation). Coolster and Massimo have the engine in the front. The X-PRO is a mid-engine, so the chain drive is much shorter and supposedly isn't as likely to throw the chain, but I don't know how often it happens with the other options. The Coolster does have a chain/sprocket guard so if you encounter a ground clearance issue, at least you're not digging the chain and sprocket into the obstacle.
We got the Coolster because we have a lot of elevation change in our property and I wanted some weight in the front to prevent a backward rollover going up a hill. I had it delivered to my parents house so I could assemble it and keep it hidden until Christmas, and they dropped it off with a liftgate 18 wheeler.
I had to mount the windshield, the roll bar, the coilovers and the wheels/tires. It definitely has all the telltale signs of Chinese manufacturing - crappy instructions, disorganized and occasionally missing hardware, weird greasy coating on the tires, and it smells like Harbor Freight. Just look at the translation quality in the troubleshooting chapter of the manual.
Christmas eve I trailered it home.
So far the issues we've encountered are that the speedometer doesn't work, it would stall occasionally when stopped and was losing fuel through the bowl overflow. I adjusted the float yesterday and it hasn't stalled since, but I haven't followed the kids on it to see if it was still dripping.
Brakes are hydraulic discs, with a single brake for the rear axle. Transmission is a sequential 3 speed with reverse and a centrifugal clutch. First gear is annoyingly low, and in third it is capable of going faster than I would want to go on it. The kids mostly use 2nd and it seems to start from there just fine as long as you're not trying to climb a grade.
On the speedometer I've gotten as far as printing off the electrical schematic. It hasn't turned out to big a big issue because the boys have actually so far shown reasonable judgement on how fast they should go just by feel.
The 9 year old fits it perfectly, but the 6 year old has to lean forward to reach the steering wheel.
9 year old driving, pictured with one of his friends that lives about 0.6 miles and three intersections away.
It doesn't seem to be as bad with the kids in it, but with an adult, the weight distribution is so rear-heavy that with the solid rear axle, the front tires will just slide on the ground with the Jeep going straight instead of turning. I might take some pressure out of the front tires to see if I can bias some grip more forward, but if it's that bad with a front engine I can't imagine what the mid-engine version would be like.
They've burned through about 5 gallons of gas so far. Did the first oil change and went over critical fasteners yesterday. Will report any future issues.