Try the guys at J & R in Butler, Ohio. They seem to have a little bit of everything. I would tend to think that all trailer steps would have the same demensions as far as width and depth. The only difference would be whether it was a one step, two step, or three step assembly. If I am wrong, hopefully someone will set me straight. Basically, the steps should be universal in size.
2014 FR Heritage Glen 282RK
2013 F250 HD 6.7L Diesel
Formerly Owned: 1995 22D Fun Chaser & 2901L Classic