Source for 13 mm hex wrench

[Paul Meyers]

I read with interest Scott Mockrey's process (www.sjmautotechnik.com) for
bringing an older 5000 up to non-vacuum-leaking status. After building an
air plug for the Michelin man hose, I pressurized the intake manifold and
discovered leaking air sounds coming from the head. Wiggling the fuel lines
going to the injectors produced louder air sounds. I decided to replace the
injector seals, etc., according to Scott's instructions. 

Rod at the parts connection sold me the parts and off I went, assuming I
could actually do this job. Scott says that you need a 13 mm hex wrench to
remove the injector seats from the head so you can replace the phenolic
inserts and the seals. OK. Off I went in search of a 13 mm hex wrench.
Nobody's got em, at least in Utah. The Snap-on guy doesn't have em, the Audi
dealer mechanics don't have em, the after market Audi wrenchs don't have em.
The specialized tools guys don't have em. So, since I was in the middle of a
job, I decided to improvise. A little math tells me that 1/2 inch is 12.7
mm, so maybe I could use a 1/2 inch allen wrench to get through the process.
It works, though it's hard to accurately torque the seats with a 1/2 inch
allen wrench ($9, Sears). Also, to actually remove the rearmost seat, you
absolutely have to remove the valve cover to have enough clearance. Sears
doesn't sell a socket-based 1/2 inch hex wrench, so far as I can tell.

Anyway, anybody got a source for a real, 13 mm socket-based hex wrench?

Paul Meyers 
Gray 87 5KCSTQ 1.8bar eurolights fuchs 145 kM, needs loom transplant 
Pearl 88 5KCSTQ 1.8bar eurolights fuchs bilsteins 125 kM 2pc-em k24 turbo 
Metallic White 87 5KTQW 191 kM daily driver
Blue 86 5KCSTQ parts car