Suitable eqivalent transformers may be available from UK suppliers such as CPC, RS, Cricklewood Electronics, or Rapid Electronics, but I haven't checked any of the websites concerned. As already stated, provided the voltage and current figures are similar to those of the original, and the physical dimensions are also the same as the original (L44mmW40mmD35mm, with FCs54mm) a transformer from an alternative source should be suitable.
Michael Goscombe, June 2016