I have found the following non-triple specific FDs to work with triple cranksets:
- Suntour Cyclone 1st gen
- Shimano Altus early 1980s
- Shimano 600 mid-80s
- Shimano Thunderbird, vintage unknown, probably early 80s
I've converted 3 double chainring bikes to triples without needing to change the spindle. YMMV.