Body-Solid Endurance B3R Self Generating Recumbent Bike
List Price: $2,675.00
Sale Price: $1,999.99
I looked around and this is the only one I found that said that the max is 400 pounds. I found it at Exercisebikes.com
I think that a recumbant bike would be good because it will allow your knees to bob up and down without discomfort.