> Is there any kind of grommet available to fit the vanagon roof? I've got a hole drilled in it and there are two layers of sheet metal at the top (close together). The hole is for a wire...

Shouldn't be too hard to find such a grommet. Your first step is to
measure. 1) what's the diameter of the wire, 2) how thick is the
metal, and 3) how big is the hole in the roof. Then go stomp around
the internet looking for what yu need. I note that Amazon lists
grommets for sale:
<http://tinyurl.com/6y75tq>

Personally, I found it was just easier to buy an assortment:
<http://tinyurl.com/638lzz>
 I added so many strange wire runs to my Vanagon that I found I used
them all the time. I bought my grommets from AutoBodyToolMart.com,
which I would now advise against. Their prices are good, but once they
get your mailing address they'll send you a paper catalog every dang
week for the rest of your life.

--
John Bange
'90 Vanagon - "Lastwagen"
'90 Vanagon GL - "Wiesel"