You wrote (in your message from Sat 6)
 > 
 > I looked all over ftp.netbsd.org and ftp.xfree86.org (including
 > downloading every file in the XFree86 3.3 binary distribution and
 > looking grovelling through them all..
 > 
 > Every bit of documentation I found on this topic simply said to take
 > the ap.o file and add it to the LKM configuration, but I don't have
 > the file or even the directory it's supposedly in.

Yes, it's missing from the XFree86 3.3.1 binary distribution for
NetBSD. Sorry.
 > 
 > I'd prefer source code to build the driver myself, unless it requires
 > a full XFree source tree to do so.

You can get the source at:
<ftp://piblic.xfree86.org/pub/XFree86/3.3.1/untarred/xc/programs/Xserver/hw/xfree86/etc/apNetBSD.shar>

It should build without difficulties on 1.2G.