I bought the one from PetEdge.com that can be used as step or a ramp. Jazzie love it! It has very wide rungs so it seems safer if its used as a step. I got the 3 step version since my bed is really high too. Super sturdy and folds flat to slide under the bed when you don't want it out.
http://www.petedge.com/shopping/prod...ProductID=5530