Whatever you get, don't skimp on getting a good holster for your carry style.
"most" guys here will likely point you to a 9MM.
Tons of good ones, Beretta, Glock, Smith M&P.......
The better/more diserable.......boom, the higher the price.
If the SR9 felt good in your hand, then I'll give another recommendation for the SR9C. Size and performance are very good.
So many choices. Have him pick.
CZ 75 with additional 22 barrel and slide?
Ruger or Smith .357 and shoot .38s?
A .32?