Welcome Panzer,
If it were metal 1/16th tracks you needed they're fairly easy to source, after a hunt I can see why you're having trouble finding 1/35th ones.
It seems they did do a version of the 1/35th RC Tiger with metal tracks:
Tamiya America Item #89628 | German Tiger I w/Metal Tracks - Late Production
But as it's discontinued & no longer figures on their normal parts lists it might be best to contact Tamiya for a spare parts number which would aid greatly in the search (ebay a likely place to look).
There are companies making aftermarket metal tracks for static models (Fruilmodel etc.) but even though they're fully articulated when made they would be
very unlikely to withstand RC type activity.
Cheers, (and good luck)
Adam.