Funny, This same subject was dug up over on the VMF today as well.
I found a CORVETTE interior guy who CAN and DOES stamp the vinyl windows for the Corvette crowd.
You have to send them your window and the service costs $75.00 per stamp.
They have all the proper company names and logos to use and can also correctly date the window as well.
They sent me a sample of their stamp on a small piece of clear vinyl, it looks pretty good-just haven't had mine done yet.
I think Brant at VA Mustang most likely has his done by now, might want to ask him how it came out.
Heres the link:
http://www.alknochinteriors.com/Also found THIS place that HAS made irons for this purpose before (most likely did Al Knoch's) and can make a fixed, non-changeable iron for around $400.00
http://www.brandingirons.com/index.html