I had an adjustable Amazon one for t16 cd dock. Different tips for polarity n size. Adjustable voltage.

Edit Something like this

https://www.amazon.com/Adjustable-Universal-Switching-100V-240V-Electronics/dp/B09NN4WTXK/ref=mp_s_a_1_4?keywords=adjustable+dc+power+supply&qid=1671599796&sr=8-4

I'm in the US, and this was the first result on my search on Amazon COM, not UK. Not a recommendation, but if I needed something like this, for $20 (USD), I'd consider it.

https://www.amazon.com/dp/B09NN4WTXK/

It should work in the UK, but the plug is different (NEMA 1-15 versus whatever you'd need in the UK)

"Input: AC 100~240V, 50/60Hz, Output Voltage can be adjusted from 3V to 24V DC (such as 3V 4V 4.5V 5V 5.5V 6V 9V 12V 14V 15V 19V 20V 24V). Wattage Max 3A, 72W; It can supply with amps less than 3A, such as 300mA, 500mA,1A, 1.5A, 2A, 2.5A, 3A."