I have 3 separate John Deere brand blades for my LA 42 inch deck. The 3n1's that came with it. Mulch blades and hi-Lift blades. But, they all sit on the shelf and I run with my Gators. You should have no problem finding the part numbers for the JD blades at greenpartsstore.com and the gators at any tractor supply store.
As far as the hi-lift blades go, they do not recommend using them without a bagger..
"Important: Use of this blade without the rear bagging attachment will result in an unnecessary load on the engine and produce poor grass dispersal."