Earlier quoted context omitted.
This is an easily solved problem. Backblaze has an example here: https://github.com/backblaze-b2-samples/cloudflare-b2
Does the solution involve using Cloudflare workers? Because, as I said, I'm sure it is possible but maybe we've gone off the deep end a bit. Just how crazy of a configuration do you want just to serve files from an object store? This looks like an awful lot of setup for "easily solved". Easily solved is what S3 does where this isn't even a problem.
curl -sL https://github.com/backblaze-b2-samples/cloudflare-b2/raw/main/README.md | head -n 1
# Cloudflare Worker for Backblaze B2
yes, it's a worker