Filters works great for this, though it will require two runs:
Searching for "type:hero" (without quotes) will only show hero cards, such as Magister Dawngrasp.
Searching for "replace your hero" (without quotes, of course) will show the non-hero cards that can replace the hero, like Renounce Darkness. Jaraxxus was recently converted to a hero card, so no longer has the "replace your hero" text.
Worth noting that, on mobile, Standard/Wild must be selected in Filters before entering a search term.