Help me find a front derailleur!

Looks like an old Deore DX/FD-M650 mounted pretty high.

That is the Shimano Deore DX, FD-M560, judging by the dark-colored insert on the outer link. You might consider a FD-M786 if you don’t mind that it’s not period-correct… this is a double-chainring model that has a short-tail cage for better tire clearance, and pretty deep inner plate. It’s dual-pull, it’ll work as either bottom-pull or top-pull. There’s also a triple-chainring variant that still has a short tail, if you see a hot buy on one.

edit to add: if you’re shopping for one, just note that there’s a direct-mount variant to be avoided.

https://preview.redd.it/mkqmd2i2jjfg1.jpeg?width=2296&format=pjpg&auto=webp&s=158eae0362d838b6079c89286e29f5067caa8596

Are those tires the 27.5×2.8 chonkers?

I used a campy FD on a friction shifter no issues, pretty cheap and polished silver which is the biggest selling point

Rivendell might have something that primitive.

Suntour Mountech 2700. 

10sp Sram: XX [29×2.6].