I'm pretty sure the entire NSA budget is classified, even the total budget. According to this Congressional Research Service report, the NSA is in the "National Intelligence Program". It says:

> The NIP funds the Central Intelligence Agency (CIA) and the Office of the Director of National Intelligence (ODNI) in their entirety, and the strategic intelligence activities associated with departmental IC elements (such DOD’s National Security Agency (NSA)).

And it later says:

> The ADNI/CFO is responsible for producing the Congressional Budget Justification Books (CBJBs) and the accompanying NIP Summary of Performance and Financial Information Report. Together, these classified documents explain and justify the details associated with each of the NIP programs to the House Permanent Select Committee on Intelligence and the Senate Select Committee on Intelligence.

I highlighted the word "classified".

The detailed President's budget request is called the "Congressional Justification" (CJ). The NSA is in DOD. I couldn't find any CJ for the NSA. It's probably classified, so there probably isn't a public version.

Useful committee hearings will probably also be classified.

If you work for the Australian government, you'll probably want to work with whomever in your agency handles international relations to get what you need to know. You're in Five Eyes, so it's reasonable they would give you some information if you really need to know.