Hmmm.
The Lexmark website states that the part number is 11B6073:
http://tinyurl.com/5k9mjj
Clicking on 'Find Reseller' produces the information that the only recognised UK vendor is EET Nordic, with a rather daunting ex-VAT quotes of �18.91 for the power lead plus a further �11.75 for the carriage. With printers being so cheap these days, it might be better to buy a new printer.
To make matters worse, the EET Nordic website seems to deny that they stock the item anyway. (Call 020 842 10101 for a definitive answer).
Take a look at the label on the device to see what the power input is shown as. If it's shown as 220, 230 or 240VAC, then there's no transformer required and Maplin Electronics might still be able to supply a lead.
If the input voltage is shown as (for example) 9V DC, then you definitely need a suitable power adaptor. It's likely to be at quite a high current rating but Maplins may still have something suitable. (My Sony Video Walkman, which I only use a a small desktop TV, recently stopped working because the power adaptor had packed up. I found out that Sony wanted �205(!) for a replacement part. I managed to get hold of a 5 amp power supply, at the appropriate voltage, from Maplin, for �20. I had to solder a connection on, because the lead didn't fit my Sony Walkman, but it works fine and saved me �185).
Chris