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Considering the age of the treadmill in question (1990s ?) and the obscurity of the component, it is possible that a replacement for it is not obtainable.
...except by taking it from another Vitamaster treadmill, e.g. one that is being discarded or scrapped as otherwise defective, obsolete, etc.
Perhaps such an old/used/scrapped/defective treadmill of that model or that model line might be found for sale or for free on
I presume the transformer in question is a component, not an AC Adapter.