If he wants to make things easy I would recommend a small battery powered elektret microphone like this:
Sony ECM-719It uses a tiny LR44 battery.
It has a clip on the back. As it is omni he can put it on his shirt under his jaw and the cable inside the shirt to make it invisible.
As long as he is silent (turning head and whispering is no problem) he can move around a bit without losing too much of quality.
It has a 'voice/music' switch and it can handle pretty loud shows.
The cable is long enough so he can have the M10 in his pocket or in his hand to check levels and stuff.
I used this mic back in my MD days when I was lazy and wanted to be stealth without external battery power. The mic is small enough to avoid attention. I always had it under my jaw, on my bag strap or hoodie. Noone ever noticed the mic. Hit and run.
I'm sure the M10 has better mics but to gain interest in taping it should be simple. To have the M10 in a hat sounds like a task even if it's small. You don't have any control at all as you can't watch the display. Doing all the work and the sound turns out too hot or maybe not recorded at all. That is a big disappointment. Any omni will pick up some audience chatter but putting it above the head won't really change that.
You can find sound samples if you search "ECM-719" on Dime.
Just a suggestion. We all need to start somewhere and making better and better recordings is a great trigger. Hope it helps.