I looked into that as well! At the end of my hunt it pretty much boiled down to this:
DogScooter.com || HOME
I might get one in the spring
I have a Blauwerk Willy scooter and I like it except my knees are too old to do the kicking. My female will not pull. So, a couple of weeks ago I bought a new bike that I can use with the dogs that's a step through model in case of accident. I think I'll get a Springer connection for my female who just trots alongside anyway.
But if I still lived in Chicago, you bet I'd get one of these sleds. LOL!
Here's the link to the Kickbike home page. There are a couple of dealers in the US and, if I didn't already have a scooter, I think I'd buy one of theirs. Their scooters have disc brakes and a nice large front wheel for stability. They look closer to the ground, also. Maybe not.
Kickbike - Kickbike Home