@cliftoncat 
and now I ran out into the rain to get a pic for you
Glad you found some.
And like Lilli, I would also like to know where you found them - you never know ....
Anyway here is the pic that you asked for.
This was just a trial and the aluminium was a little to narrow for the tape - only 10mm wide - but you can see what the clear tape with black print looks like on the aluminium. Will probably look just as good on the galvanised markers.
