In jazz, the term altered chord, notated as an alt chord (e.g. G7alt ), refers to a dominant chord, in which neither the fifth nor the ninth appears unaltered—namely, where the 5th and the 9th are raised or lowered by a single semitone, or omitted. Altered chords are thus constructed using the following notes, some of which may be omitted:
root (typically omitted by comping chord-playing instrumentalists)
3rd ♭5th and/or ♯5th (the ♭5th is often expressed as ♯11)
From : https://en.m.wikipedia.org/wiki/Altered_chord (Lots more discussion there)
In iReal pro, the player accepts x9#5 (the closest to a whole tone chord), x7#5, x7b5, x7#11 and x7alt.
Until your requested chord can be played by the player (for reader charts you can already write it) your best choice in specific situations can be selected from this example chart: