How to get blurred mirror effect in webGL?

So I’ve been all over the place on this, and thought I had it. I’m looking for a way to make a reflective surface that’s somewhat blurry, and has to run in webGL builds.
I tried a reflective shader, putting a Blur effect on it, looks great in the Editor, crashes in webGL.
I tried using a ReflectionProbe and Standard Shader, but the reflection is really jaggy, even when blurred. Maybe I’m using the wrong settings.

The current WebGL is based on OpenGL ES 2.0 and its limitations so you might have to adapt your shader to that.