10 X more than you need, but yes; that would work. Any piece of paper that says "Fit to Fly" with a scribbled signature and maybe a stamp would probably work. However, it does need to be from a legitimate source.
Misleading info thru out the responses. 72 hrs before flight is RESULTS; NOT the Test. Be sure you are NOT doing the Rapid test; must be RT-PCR; but quick turn around time would be a good thing. The Fit 2 Fly must also be done within 72 hours of departure, but is independent of from the RT-PCR test.