The handle on the case can sometimes be repaired, Singer had different handles over the years. If it has leather straps you can find new leather. The old screws can be taken out, and they fill the holes with fine sawdust and wood glue (poke and pack it in there best you can with a tooth pick), then have the screws back in. Maybe find slighly wider screws. There are youtube videos on how to fit new handles. I think there's brand new Featherweigh cases available, very much like the original ones.
For the feet and accessories you can get inventive; in shops for fish flies and hooks they sell boxes with multiple compartments, some are ideal size for the low shank Singer feet. There are more general storage boxes in wood or plastic to keep all kinds of small items organised. There are are one and two layer
jewlery boxes that can be used, tea boxes, etc...