Bafang Motor Parts
CYC Motor Parts
Complete Custom Bikes
Since it was a fat bike conversion, my guess is that he used a Bafang BBSHD since those come in wider bottom bracket widths. The Bafang BBS02 on fits bottom brackets between 68-73 mm width. The BBSHD starts about $700 just for the motor kit I think.
he has a video on it you can look up.
I saw vid, he didn't say which motor is it a complete kit? He refered to a 52 volt battery was all.
if u see his vids there are lots of mix and match, diff batteries with different motors, its all about what u need. u pair a battery (generally 52v) with a motor, figure out your range needs and power u want. simple. check his shop link to see motor and battery prices, thats all that there is in a 'kit'