Roger Whiter's framebuilding blog
Some time ago I discovered a nice little 531 Orbit frame discarded because it had a snapped off drop out.
I made templates by tracing the good side
I marked out the pattern onto a piece of steel plate and by drilling, hacksawing, and filing fabricated a replica dropout.
Not sure if I got one of the angles right on the top bit, so I may have to do this again. It’ll be easier to see if this is true once I get my jig made.