Work out the make and model of your exercise machine then use Google or a similar search engine with the search term (your machine) service or (your machine) spares you should be able to find a specialist or a spare part supplier.
Yellow pages "exercise machines" or "gym equipment" might also be useful.
Good luck...
Peccavi
March 2013
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix gym/fitness equipment.