[Legitimate] Digital Copy of Joker?

Does anyone know where I could buy a (legal/legitimate) digital copy of 'Joker'?

iTunes and Google Play both have it for $25, but I just really hate that it's priced higher than a DVD. I'd buy a DVD but have no way to watch it on my iPad). I'm not really sure of anywhere else I could buy a digital copy (except alongside a BluRay version…but I also don't have a BluRay player).

So…does anyone know of anywhere else that sells digital copies of movies?