I know for a fact that mini grovers do come in black

It's more of a shiny black, which they call black chrome or something similar.
To answer your question, most of the time grover has a gotoh counterpart and vice versa. When the issue is the hole size and dimensions, people generally call "Crover/Gotoh". So I am guessing you should be ok. But, don't take my word for it. Grover has exact dimension at their website, I am sure gotoh has them, too.