Does anyone know a good way to shop for flights with mixed classes? For example - flying business outbound & economy return?

I know some carriers make this easy - like Swiss (depending on connections) will show you all fare options from eco to first for each flight. I'm specifically looking for LH right now, but this comes up every 6-12 mos for me, so I'd like to find a website that will do it for any carrier.

Thanks.