key resellers have office 2021 pro plus (the non subscription one) for $30.00ish (earlier versions are even cheaper) and that is what I recommend if you absolutely have to get office.
Considering the grey market is filled with dodgy keys, it'd be better to just pirate, especially when there are easy and safe ways to do it like with MAS
imho between the two options, the more ethical is to pirate rather than supporting a shady key reseller. Anyway microsoft gets the exact same amount of money either if you purchase a stolen key from msdn or you install a pirated copy activated via mas