Angelcare power adaptor

We have an Angelcare baby monitor. The power adaptor connector has
developed a problem. Basically it's very difficult to get it to stay
on, as you have to arrange the cable at just the right angle.
Does anyone know if we would be ok using an off-the-shelf 9V power
adaptor like the ones you can buy at Argos or Maplins?
I don't want to break the unit as it isn't cheap!

Thanks.
Andrew.

.