Signs and leaving marks on chain link fences

The homeless dudes who make the park home are definitely influencing the process/piece...

Tags for the Fence

I am looking for something interactive to leave behind on the chain link fence:
choice #1= cheap and audience can write on them
writable metal rim tags
choice #2= not so cheap but cool and engrave-able
metal valve tags

The space has greened up incredibly in the past week. Much more lush. And many more lushes to go with the warm weather....