There are some on AliExpress. I did a quick search for "SA keycaps", and there's one with the description "104 Keys/set SA Height New Arrival Double-Shot Backlit Ball Keycaps PBT Key Caps For Mechanical Keyboard" that comes in black, white, red, or blue. It's hard to tell what the profile is, but the top row does look like it's angled towards the user, so it's probably not uniform row 4, or whatever it was that Filco had SP use for their SA keycaps. I have a set of SP's newer sculpted PBT SA Industrial keycaps, and they're wonderful.