Hawkie - are you in Australia? Anyway, Polygon bikes are sold here, see this website for their latest offering:
http://www.bicyclesonline.com.au/pol...shimano-altus/.
Providence likely Taiwan, suggested by the Polygon website:
http://www.polygonbikes.com/ww/about. Your machine 10 or 15 years old is my guess.
If it fits and it goes, it's the gear.