I bought a set of floor mats 2nd hand, but he didn’t have the grommets.

Do these work as an alternative?

Here is where they are located in an interior diagram.

 

These are common across the entire Honda/Acura line and fit in a nominal 1/2" square hole -- got the holes? What's in the holes now? They're probably still in the holes of the original buyer's car. At 70 cents each there's no risk if they don't fit. Try your local Honda dealer rather than spend $10 to ship them.

-- Chuck