Replacement exam certificates must be requested via the exam board.
There are six examination boards in England, Wales, and Northern Ireland:
AQA (Assessment and Qualifications Alliance)
CCEA (Council for the Curriculum, Examinations and Assessment)
City & Guilds.
OCR (Oxford, Cambridge and RSA Exams)
WJEC (Welsh Joint Examinations Committee)
Contact details are available via the exam board website.