Drivers? I'd call the manufacturer, Okidata, and ask them. You're going to have to spell AIX for them and they aren't going to be able to provide you with anything, but if they get enough calls maybe they'll start thinking about support for various flavors of Unix.

Unfortunately, this printer does not appear support PostScript. The good thing about PostScript is that it is device independant. A "driver" for PostScript Level 1 should work on all PostScript printers; a driver for PostScript Level 2 should work for all PostScript printers that support Level 2 (i.e. Version 2) or better. Okay, a given printer may support some superset of the level 2 commands, etc., but generally speaking, by sticking with PostScript you can avoid having to deal with drivers (Windows used to come with a driver for "Generic PostScript" and why it doesn't anymore is a mystery to me...).

You can try various models of HP color printers and see if any of those work, and it is probably worth your while to do so, but something that may also work is getting Ghostscript (http://www.gnu.org/). Ghostscript is a program that will do various things with PostScript, and one of the things you can do with it is set it up as an output filter on a print queue so that it translates from PostScript to PCL. Haven't had to do it myself; I hear it isn't fun, but that may be another option. Then you would use a "driver" for just about any color PostScript printer. Your print job will get translated into PostScript by the driver you choose, and then Ghostscript will translate it into PCL and hand it to the printer.

I know, as Unix admins, we aren't always in on the purchasing decisions about printers, but I've worked very hard at convincing those who do that there are two kinds of printers in the world - printers that hang off of the newtork, do PostScript, and speak the LPD protocol (it can speak other stuff too, but Unix, PCs, Mainframes, AS/400's; darn near everything can speak LPD), and printers that are junk.