Best place to trade cash ~20 000 USD$ to Yen?

I tried finding this answer in previous post but there did not seem to be a definite answer and most post were a bit dated.

Back in Canada my Bank would offer me preferential rates when I traded over 15 000 USD to CAD at once, is it possible to have a similar arrangement here? If not what's the best place to go?

Wife has an accounts at Mizuho.