Without having the engine in hand – I assume the tender trucks are part of the electrical pick up? There are other makes of such trucks that, assuming the bolsters are compatible, would work. Search the Walthers catalog, as well as Bowser’s.
Mantua tenders are pretty common items at swap meets and often a tender intended for a different locomotive will substitute just fine, as well as giving the engine a different look. Old Model Die Casting and Bowser tenders migtht also substitute.