Recommend a copper marker brand?
 

I'm tired of going out to my beds and finding broken plastic and eroded
print, so I've decided to move to metal markers. Can someone recommend a
copper label/marker manufacturer and a place to order them online?
Requirements: a) decent quality, doesn't easily break , b) goes at least 8"
into the ground so heaving in spring doesn't push it out of the ground, and
c) is somewhat affordable (say 50-75c a piece).

I am assuming here, perhaps incorrectly, that engraving to copper is better
than using zinc markers with a crayon (such as those offered by
everlastlabel.com). I'd be curious to know which is easier to read and
which is more permanent.

Thanks for any help.