Austin has DIY-from-scratch instructions:
http://diyribbonmic.com/
I think he may have a 3D printing template somewhere, actually, since he started doing those.
Be aware that cutting a ribbon even with the right tools by hand can be very challenging, it took me a few hours the first time and it wasn't quite right (I eventually fixed it, then messed it up again later).
It's also not exactly a cheap project; the transformer is fairly expensive and unless you're doing your own metal working, you're going to need a body.
While I like the Austin I built (and the guy who runs the place is incredibly nice and helpful), I do somewhat prefer the RM-6s I built: http://www.diyaudiocomponents.com/
But those barely qualify as a DIY project, it's just a couple soldered points and assembly. But the RM-6 sounds fantastic so it's hard for me to feel bad about "cheating".