Sadly VB and Moss (U.S.) don't support the Mini. Moss Europe does support the Mini "over there". You can use a lot of Midget parts and both those vendors have catalogs for those cars.
I'm not sure Seven has printed a new catalog since they moved to CA from VA. Prior to their move they hadn't printed a catalog since 1995. Even if all they have are copies of the old 1995 catalog, that one is worth having as a reference.
I believe Mini City will sell you a catalog. Theirs is/was in a three-ring binder. The prices haven't been updated in years and a lot of parts are marked NLA but it's still a good reference.
Mini Mania may not have a printed catalog either but I believe you can request a catalog on CD. At one point this was free with an order placement. I don't know what their current policy is.
There is also a Heritage CD available (at Mini Mania definitely... probably available through Seven). It includes PDF copies of the factory service manual and many exploded drawings. It's a very good reference to have.
It appears that most everyone has gone digital with whatever catalogs they offer.