How do I check if a project file exists, by name?

"Request URL" works because that takes a string, unlike "Request project file". I can then compare the status code to see if it exists. However, this grabs the entire file; I just want to check if it exists. I tried "Set request header" with 'Header' as 'type' and 'Value' as 'HEAD', but it still fetched the entire file. Any ideas?

I posted a suggestion a few years ago for "Is project file exists" condition, but it was declined.

Actually, I'm trying to do this for audio files which I can't figure out how to get with "Request URL" (can't use ../ to go up from the "Files" folder) but the following seems to be working (counting how many variations of an audio track exist, so I can play an random one)

For reference the feature request was filed here, where I provided a justification why I don't think it is worth implementing, and what you can do instead.