I don't know where he finds the time / strength / energy / courage //
money to ...
I haven't the time / ... to ...
are common in English. They can be considered as deletions, probably from
I don't know where he finds the time needed / he needs to do all he
etc. They are grammatical. However, substituting other comparable terms for resources
(?I don't know where he finds the composure to ...
*/? I haven't the bravery to ...
I haven't the readies to ...)
often produces results sounding distinctly weird.
I haven't time to do that today.
is also acceptable, and here means the same as the version with the definite article. But there can be subtle differences. We wouldn't normally say 'This job keeps me so busy that I haven't time to fly home every weekend' or 'Because the taxi is so late, I haven't the time to catch the train'. But 'I haven't courage to go so near the edge' is non-idiomatic and possibly unacceptable.
Where did he find energy to fight so many times?
also sounds unidiomatic. You could probably get away with
Where did he find time and energy to fight so many times?
with proximity persuasiveness winning over correct parallelism. But I'd say that with energy preceding time, the version with the definite article would be far better.