Can I use a 6v dc adaptor for 6v ac?
You can try to do the following operation with the help of a professional/someone who knows what she/he is doing:

You can buy a transformer with a ratio of primary turns/secondary turns of 36 or 22 depending on what is your outlet voltage from a local electronics shop.If you take care of the current ,too,it's probably not that hard to create the needed supply.Connect the 110-220V to the socket and the 6V directly to the phone's input.

You need isolation from the mains in order to prevent shock and that's why I suggested the experienced partner.Outlet voltage is dangerous.Don't play with it.