If he's exceeding the max SPL of the capsule, no pad will help.
Turning the gain down is the first thing to do.
If it's at minimum, look for a pad on the interface/mic pre.
If there isn't one, choose a different mic or look for some inline pad options on line.
You can get them pretty cheap.
If you're handy, you could make one in a couple of minutes with a few resistors.