You've got several options, as Sterling Silver is a common handle material (look into Tiffany's or any of the old English Silver Hallmarks). If you want to keep it pure sterling, I suggest you use it only as an inlaid with matching nickle silver bolsters, on top of a stainless steel layer. That way when you inevitably take the polish cloth to it, at least it'll shine up nicely. And the nickle silver will protect the sterling silver from the typical impact damage of flipping balis. This will also ensure all connection points are not directly attached to the soft silver metal, as all stress points will be connected to the steel underbody.
However, if you want to use the silver for entire handle (as in non-inlaid), I'll go with a silver alloy. Not sure what the correct metallurgical terms is for alloyed silver (much like 10K gold) but they will allow for a stronger base material than pure silver metal for bali handles. This way you'll get a bali with the high polish sheen of silver, but the stronger characteristics of an alloy. I'm a little weary about using pure nickle-silver as a handle material, as it is a little soft (harder than sterling silver, but still soft nontheless), and can get expensive in the bar sizes required for a channel milled bali handle (if you can find any), but are readily available in sizes for a sandwich construction bali. There are, however, several different flavors of nickle-silver, and you might be able to find one that statisfies your needs.
Good luck, and keep us posted with your progress.