You could try this email:

mobiiliasiakaspalvelu@dna.fi


="mobilecustomerservice at DNA.fi"

Don't know about availeability, but they have so many shops in the greater metropolitan area, that at least one of them is bound to have some in stock.


EDIT:

Found some direct email addreses to their shops.

These three are at central Helsinki.

helsinki.kamppi@dnakauppa.fi
helsinki.kaivokatu@dnakauppa.fi
helsinki.sanomatalo@dnakauppa.fi

This one is just outside the airport area:
vantaa.vantaanportinkatu@dnakauppa.fi