I have the linear supply already, I just needed to make the cable up for it, just waiting for the eBay seller to get back to me.Chris
As I said, look at the rating label and tell us whether it shows the +V connection is to the centre pin or the outside of the connector of the box power inlet.
Then on ebay you can find a range of suitable PSUs, e.g. 18v 1.0 in Computers, Tablets and Networking | eBay.
PS: many laptops use a 19V o/p PSU, and that should be fine - the voltage difference is negligible!
PS2: and, Yes, I know you have found a suitable connector!