This one looks like it is IR controlled so if you had an IR blaster that could work.
Sphero is quite a bit more expensive but they appear to have an API and a quick search shows a bunch of libraries to get Sphero to talk MQTT.
Several of the higher end robovacs have APIs that I know of.
That’s all I can think of but I’ve been looking a bit. My five-year-old really wants to build a robot and I’m looking for project bot like this. I’ll be watching this thread.
I’ll not be watching Vincent’s project thread, at least not from work.