If your headlight bowl is beyond redemption the first port of call is the parts books. Virtually every manufacturer used just a few headlight bowls over a wide range of models. As a rough rule of thumb if the basic dimensions are the same chances are it will fit, simple as that. Even borrowing a similarly diseased reflector to your own from another model may very well open up more possibilities to you. For example a Yamaha RD200 reflector may very well have been used on various trail and commuter bikes of the period… something else will normally fit. And if it doesn’t then there’s always the replating alternative. Google headlight re-silvering and check your options; it’s not necessarily cheap but at least it’s an option.