To begin with I would scour the likes of eBay and Amazon looking for the correct power supply that would have originally come with the laptops and pay between £7 and £25 without even knowing if the laptop(s) worked or not!
Then, it suddenly dawned on me, there must have been some Universal Laptop Power Adaptors 'back in the day' - I wonder if I can find some on eBay...
Just in case you want to try and get hold of some yourselves, here is a list of the part numbers of the Universal/Replacement Laptop Power Adapters that I have:
72W DC (Car) Adapter - CUC0001B
75W AC (Mains) Adapter - CUA0002B
90W AC (Mains) Adapter - CUA0001B
90W AC Dell Laptop Power Adapter - LPDELL12
90W AC Lenovo Laptop Power Adapter - LPLENO17
(Despite its name, the Logik Lenovo Adapter works with other makes too).
150W AC Power Notebook Adapter - APA08EU
Although these model numbers are no longer manufactured, every now and again 'New Old Stock' seems to turn up on eBay and that's what all these are/were, new but old stock and were never used until I got them - in fact at the time of writing this I have two more 2-Power NOS power adapters on their way to me in the post! It's amazing what you can find if you look hard enough.