There's only one place to get Oscar's feet.
I'll see if I can see what is missed.
Talk to Oscar about everything.
Find out that he needs part XZ2005-B for feet.
You get a punch card.
You used the forklift just outside Oscar's room to bring material to the factory.
You turned on the power to the assembly line using the room at far corner of the factory.
Control panel -
Insert Oscar's punch card in the slot at bottom center of the panel.
Pull down the lever for assembly line 3 (only one that works) at bottom right and the light will turn on.
The lever on the left of the punch card selects the skin tone of Oscar - flip the lever to select tan color (selections are tan, white, brown and mottled brown).
If you've done this - maybe best to go back to a saved game and redo - it might jar something.