Cap screw, olds valve

[Macbone1]

Just like countless school band kids back in the 60s and 70s, l have lost the little screw that says OIL which goes on the valve of my Olds Opera.
Does anyone have this part lying around? If so, I'd be willing to buy a baggie of two or three in case I lose another one.
This part is interchangeable across Olds trombone models, doesn't have to be off another Opera.

[Posaunus]

Olds had a great idea to label the thumb screw "OIL." Very helpful as a reminder of where to apply lubrication to the valve's back bearing. Too bad they replaced these with simple slotted-head screws (which require a tool!).