Are you on about the cash box door at the bottom of the machine? Sounds like you have got a “Securdoor” (ie., the whole door lifts away when you open it). You can change the door with a standard type. Just be aware though that coin and cash box doors do vary in size very slightly (even though they look identical). Usually it’s either a Mars or Coin Controls type (I think the Mars is very slightly bigger) and there are other types as well. Unless you have a selection of spare doors to try, it’s often easier to find one complete with the frame and replace both.