Mattress wanted to borrow or buy

Hi everybody, I'm rather urgently looking for a mattress to buy, borrow or for free.

It is to replace the broken one our rental accommodation came with. When we moved in the letting agency acknowledged that it wasn't fit for use and arranged for its disposal; however, they are dragging their feet to replace it because our tenancy is coming to an end in a month's time (I was using a spare mattress of our own upto now).

If somebody has one they aren't using at the moment / anymore I would be extremely grateful.

The bedbase is a standard double (137cm x 190cm / 54" x 75" ). Anything that fits onto that.