After wasting half the day searching every forum and cnc parts site I can think of it appears that dumpstercnc has the exact anti-backlash nut I need. I dunno if practical bought from him or he just happens to have the same part (http://www.dumpstercnc.com/acme_12102.html part#AC12102-LN, with the .980 flange).
I see he hasn't posted here since Oct. 2008. Does anyone have a phone number or some way to get in touch with him? I sent an email and haven't heard back yet. Otherwise, any other sources for the parts?
I've also called Josh (formerly of Precision Automated aka PracticalCNC) and left a voice mail asking where to get one of those doohickeys. Due to my experiences with his former employers I don't hold much hope of a return call.
Of course the machine is smart enough to only break down when it's crunch time and we've got several big jobs due to be installed like right now. Ugh.