MIT is behind plenty of interesting robots. You can’t exactly go and buy them though. You can always find clones of those robots on sites like Alibaba. This MIT Cheetah Quadruped Robot Clone has max load of 3.5kg capacity and can walk, run, backflip, climb, and do a whole lot more.
The robot is compatible with Windows, Linux, and ROS. It can continuously walk for 90 minutes or stand in 3 hours on battery. The bad news? Something like this doesn’t come cheap.