I second the recommendation for Bahco. I bought one of their adjustable wrenches on the basis that it would last, and I have no regrets: it's an incredibly well made tool.

For other options, there is a youtube video comparing different adjustable wrenches for strength (https://www.youtube.com/watch?v=cyOd05PUix4). The Bahco did indeed do well, although it was not the very best the tested.