I see more broken tops than I do bottoms on the bentwood cases. If you still have all the pieces of the broken bottom you can glue it back together. If not, it may be worthwhile to find a new bottom for it to match the top. You may also be able to find a couple cheap junker machines with good cases at your local thrift store and use the cases from those. I don't like plastic cases on vintage machines but failing the above options a generic new plastic case will at least protect your machines. I just bought a 99 that needs a case. I plan to build a new case (not a bentwood) for it like the vintage cloth covered ones from the 50s. I'll post a tutorial when I do.
Rodney