code leveraging Buffer-specific methods needs polyfilling, preventing many valuable packages from being browser-compatible
... so don't rely on it.
If the methods are helpful then reimplement them (as a library, even) and use that in your code. When passing data to code that you don't control, use the underlying ArrayBuffer instance.
The very mention of polyfilling here represents a fundamental misapprehension about how to structure a codebase and decide which abstractions to rely on and which ones not to...