Morris Column Posters - available for sale?

Hola.
Accidentally asked this in r/Barcelona (sorry). I'm hoping this is the right place : )

Can I buy the posters that are put in the Morris columns in Barcelona? (These are the round circular billboards in the street.)

There are some great band posters from gigs I've been to, and I'd like to know if they're available somewhere (I've had no luck with Google on this one).

Merci.