I'd think finding an older model Shimano cartridge BB with removable drive side cup would be easier than finding a good condition Swiss BB. You can mount a Shimano unit using Phil Wood cups, which is a good deal less $ than a full Phil unit. Of course, you'll still need the Phil mounting tool(s).
wrk101's suggestion sounds good on paper but you could spend an awful long time looking for a decent French donor bike for a good price, and then it still might have a French BB, not a Swiss one.