See your specialist. There is such a large variety of prosthetic devices. You would be best to consult your prosthetist for the best advice on which device would be the most beneficial and support your weight without causing further damage.
A Custom Prosthetic. Due to unique body parameters of overweight individuals, a person who is very heavy should only be fitted with a prosthesis, which is custom fit to that patient's dimensions, taken from a proper bodyform casting and stump shaping, particulary of the boot portion of the prosthesis. The foot extension below the boot may be of any commercially available design.