We actually have a big on going case at Iowa State with a cat that has 2 prosthetic legs. We just had a case presentation on him. I learned not everyone will go down that route and it is very expensive (like $6000/leg). You can google Vincent the cat at Iowa State. The clinician that helped with the case was Dr. Bergh and she talked a lot about AO foundation during her talk. From what I gathered there is not a specific company that just makes prosthetic legs for animals, it is the human companies scaling it for animals. This is probably due to cost. Vincent (the cat) his legs were donated, but the owners paid for all the other care, which I am sure was thousands of dollars.