Archival plotting on mylar

[Ethan Dicks]

I was researching how best to plot out a map or two on my HP
Draftmaster II, when I ran across a page about plots and storing them
for decades as surveyors are required to do...

http://www.aocweb.org/surveyors/archival.htm

It got me to thinking about my own project - essentially a map on a
light box (there's more to it, but that's all the map is about).  I
was thinking of plotting on mylar, but I was unable to find any HP
plotter pens with permanent ink for anything other than paper.  Has
anyone on the list here had to do any archival plots for surveying?
I'm sure that whatever products they are using would be more than
sufficient for my purposes.

Thanks for any pointers,

-ethan