If you have a cap of $900, that will eliminate some. The Mike Warren ANH was well over that when I ordered from him, but his ESB should be in your price range. The Quasimodo (ANH, ESB, or ROTJ) should be in your range as well. I don't know about some of the others.
In general helmets with lineage to the Rick Baker mold go for around $1500 finished. The Mike Warren ANH has lineage to this. His ESB has lineage to an ESB stunt helmet.
Some people sell raw casts. You could leave it as is, finish it yourself, or pay someone else to finish it.
I have a Quasimodo ANH and a Mike Warren ESB. I can highly recommend both.
A big decision is which version you want. ANH is usually much more beat up looking than ESB or ROTJ. Obviously this is an expensive purchase, do your research so you make a good choice.