I'm always saying that good modellers don't get everything right first time, but they can cope when things aren't perfect and need a little rectification.
This is a good example. I was working on a whitemetal wagon kit that had lain part-built for years in a cupboard. As I fit the brake gear, I find that a lever guide is missing.
Disaster. The manufacturer has long since ceased trading too.
Not to worry. A bit of scrap etch and a few minutes with some pliers and I've bent up a suitable replacement. It's missing the holes for the pin because I was in a hurry and didn't drill them, but otherwise it looks OK. When the model is sat on a layout, I bet no-one notices.