This sounds like an ideal use case for modshim [0]
One of its intended use cases is bridging contribution gaps: while contributing upstream is ideal, maintainers may be slow to merge contributions for various reasons. Forking in response creates a permanent schism and a significant maintenance burden for what might be a small change. Modshim would allow you to create a new Python package containing only the fixes for your bugbears, while automatically inheriting the rest from upstream httpx.
One of its intended use cases is bridging contribution gaps: while contributing upstream is ideal, maintainers may be slow to merge contributions for various reasons. Forking in response creates a permanent schism and a significant maintenance burden for what might be a small change. Modshim would allow you to create a new Python package containing only the fixes for your bugbears, while automatically inheriting the rest from upstream httpx.
[0] https://github.com/joouha/modshim