Heres a basic listing of stuff you can get...
Ruby Jango- looks like a floppy pancake
Ruby Jango deluxe - same as above.... slightly better paint job i think
Don Post 1997 - you can get a good one, but they tend to warp really easy and you end up with "anteater fett" 
DP 96 - probably you best bet... not as prone to warping as the 97 and cheaper than the exorbant prices being charged for 95's
DP 95 - Good flare, not bad warping, overall a pretty solid helmet (not perfect of course)
fiberglass recast of any of the above - good side is... since its FG it won't warp but if the helmet used to make the mold had warpage its not gonna be all that great so watch out.
Custom sculpted helmet - you don't really need one for a custom fett, but these babies are worth every red cent you lay down for em.
Thats about all I can think of right now 