Sewingpartsonline.com has belts.
I have several of this model - I am very fond of it. It is very straight-forward to operate and hard to mess up. ((I also own Pfaffs and Berninas. 1980s era. - so I do have something to compare them to.)
You will probably need a new bobbin winder "tire", too. That is under the top"lid" That tends to deteriorate and then the bobbin winder thing won't turn. The bobbin winder "tire" is very inexpensive. That can be changed "at home".
Sorry - don't have any suggestions on where to take it.
PS - Welcome to the board.